If that can be done with a formula, I don't know how. It certainly can be done with VBA though. I set up a sheet as you described:
<tbody>
[TD="align: center"]1[/TD]
[TD="align: center"]WE Date[/TD]
[TD="align: center"]Product A[/TD]
[TD="align: center"]Product B[/TD]
[TD="align: right"]30/9/2019[/TD]
[TD="align: right"]31/10/2020[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]2[/TD]
[TD="align: right"]31/12/2018[/TD]
[TD="align: right"]60667[/TD]
[TD="align: right"]61152[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]3[/TD]
[TD="align: right"]31/1/2019[/TD]
[TD="align: right"]43996[/TD]
[TD="align: right"]52628[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]4[/TD]
[TD="align: right"]28/2/2019[/TD]
[TD="align: right"]6563[/TD]
[TD="align: right"]36180[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]5[/TD]
[TD="align: right"]31/3/2019[/TD]
[TD="align: right"]67431[/TD]
[TD="align: right"]65401[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]6[/TD]
[TD="align: right"]30/4/2019[/TD]
[TD="align: right"]62530[/TD]
[TD="align: right"]31532[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]7[/TD]
[TD="align: right"]31/5/2019[/TD]
[TD="align: right"]25130[/TD]
[TD="align: right"]58111[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]8[/TD]
[TD="align: right"]30/6/2019[/TD]
[TD="align: right"]21161[/TD]
[TD="align: right"]20392[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]9[/TD]
[TD="align: right"]31/7/2019[/TD]
[TD="align: right"]72953[/TD]
[TD="align: right"]29917[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]10[/TD]
[TD="align: right"]31/8/2019[/TD]
[TD="align: right"]45347[/TD]
[TD="align: right"]40353[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]11[/TD]
[TD="align: right"]30/9/2019[/TD]
[TD="align: right"]47088[/TD]
[TD="align: right"]19899[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]12[/TD]
[TD="align: right"]31/10/2019[/TD]
[TD="align: right"]12007[/TD]
[TD="align: right"]31616[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]13[/TD]
[TD="align: right"]30/11/2019[/TD]
[TD="align: right"]20347[/TD]
[TD="align: right"]63457[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]14[/TD]
[TD="align: right"]31/12/2019[/TD]
[TD="align: right"]64445[/TD]
[TD="align: right"]30394[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]15[/TD]
[TD="align: right"]31/1/2020[/TD]
[TD="align: right"]51343[/TD]
[TD="align: right"]42754[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]16[/TD]
[TD="align: right"]29/2/2020[/TD]
[TD="align: right"]17912[/TD]
[TD="align: right"]40385[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]17[/TD]
[TD="align: right"]31/3/2020[/TD]
[TD="align: right"]42382[/TD]
[TD="align: right"]56656[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]18[/TD]
[TD="align: right"]30/4/2020[/TD]
[TD="align: right"]11876[/TD]
[TD="align: right"]48569[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]19[/TD]
[TD="align: right"]31/5/2020[/TD]
[TD="align: right"]37084[/TD]
[TD="align: right"]68953[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]20[/TD]
[TD="align: right"]30/6/2020[/TD]
[TD="align: right"]19998[/TD]
[TD="align: right"]71211[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]21[/TD]
[TD="align: right"]31/7/2020[/TD]
[TD="align: right"]64036[/TD]
[TD="align: right"]50609[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]22[/TD]
[TD="align: right"]31/8/2020[/TD]
[TD="align: right"]69359[/TD]
[TD="align: right"]45469[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]23[/TD]
[TD="align: right"]30/9/2020[/TD]
[TD="align: right"]49787[/TD]
[TD="align: right"]34811[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]24[/TD]
[TD="align: right"]31/10/2020[/TD]
[TD="align: right"]10979[/TD]
[TD="align: right"]24733[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: center"]25[/TD]
[TD="align: right"]30/11/2020[/TD]
[TD="align: right"]48152[/TD]
[TD="align: right"]70693[/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
[TD="align: right"][/TD]
</tbody>
(This code assumes that values entered in your "start date" and "end date" cells will be month ending dates)