Subtracting cells

[Asquare]

I want to subtract cell D3 from cell D2 but only if cells B3 & B2 have the same value. if cells B3 & B2 are not equal, I want the formula to detect the next two cells that contain the same values and subsequently deduct their respective values in column D. In this case the values in cells B5 & B4 are not equal, hence the formula should check cells B5 & B6 and if they contain the same value deduct the values in cell D6 & D5 (D6 - D5).

Thank you in advance.

Column B	Month	Column D	Value
900	01-Jul-15	8140	8140
900	01-Aug-15	14999	6859
900	01-Sep-15	20978
901	01-Jul-15	9000
901	01-Aug-15	14633
901	01-Sep-15	19715
902	01-Jul-15	8338
902	01-Aug-15	12799
902	01-Sep-15	17059
903	01-Jul-15	8913
903	01-Aug-15	13960
903	01-Sep-15	18475

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[Tetra201]

Is this what you need?

=IF(B3=B2,D3-D2,"")

 

[Asquare]

Not quite, When B3<>B2, I want the formula to search for the next consecutive cells in column B that contain the same values. say B3<>B2, so the formula should check if cell B3=B4 and deduct D4 from D3.

Thanks for the help.

 

[Tetra201]

Then could you please post a sample dataset with all expected results?

 

[Asquare]

Number	Month	End	Value
123	Jul-15	5057.96
123	Aug-15	9319.94	4261.98
123	Sep-15	13035.12	3715.18
123	Oct-15	14216.97	1181.85
123	Nov-15	16025.78
123	Dec-15	19130.77
123	Jan-16	24595.73
123	Feb-16	28733.44
123	Mar-16	33127.77
123	Apr-16	37580.52
123	May-16	38464.11
123	Jun-16	41100.58
123	Jul-16	42997.01
123	Sep-16	48713.00
123	Oct-16	51867.08
123	Nov-16	52919.68
321	Jul-15	5592.34
321	Aug-15	9092.52	3500.18
321	Sep-15	12250.33	3157.81
321	Oct-15	16145.08
321	Nov-15	18845.56
321	Dec-15	19392.99
321	Jan-16	21799.56
321	Feb-16	26165.31
321	Mar-16	29292.05
321	Apr-16	32028.57
321	May-16	33023.38
321	Jun-16	35753.69
321	Jul-16	38326.16
321	Aug-16	42172.45
321	Sep-16	44858.02
321	Oct-16	47721.29
321	Nov-16	48432.14

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[Asquare]

I am trying to calculate a value for every month. say august, the expected value will be end of Aug - end of Jul, July value should be ignored but I don't want the formula to depict that as July values will come automatic.

 

[Tetra201]

It is still unclear why there are no Values for Number 123 from Nov-15 through Nov-16.
Same for Number 321 from Oct-15 through Nov-16.

 

[Asquare]

Number	Month	End	Value
123	Jul-15	5057.96
123	Aug-15	9319.94	4261.98
123	Sep-15	13035.12	3715.18
123	Oct-15	14216.97	1181.85
123	Nov-15	16025.78	1808.81
123	Dec-15	19130.77	3104.99
123	Jan-16	24595.73	5464.96
123	Feb-16	28733.44	4137.71
123	Mar-16	33127.77	4394.34
123	Apr-16	37580.52	4452.74
123	May-16	38464.11	883.59
123	Jun-16	41100.58	2636.48
123	Jul-16	42997.01	1896.42
123	Sep-16	48713.00	5715.99
123	Oct-16	51867.08	3154.08
123	Nov-16	52919.68	1052.60
321	Jul-15	5592.34
321	Aug-15	9092.52	3500.18
321	Sep-15	12250.33	3157.81
321	Oct-15	16145.08	3894.75
321	Nov-15	18845.56	2700.48
321	Dec-15	19392.99	547.43
321	Jan-16	21799.56	2406.57
321	Feb-16	26165.31	4365.75
321	Mar-16	29292.05	3126.74
321	Apr-16	32028.57	2736.52
321	May-16	33023.38	994.81
321	Jun-16	35753.69	2730.30
321	Jul-16	38326.16	2572.48
321	Aug-16	42172.45	3846.29
321	Sep-16	44858.02	2685.57
321	Oct-16	47721.29	2863.28
321	Nov-16	48432.14	710.85

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There you go

 

[Tetra201]

... There you go

Unless I am missing something, the formula from Post #2 does provide the expected results.

If needed, rounding to whole cents can be added like this:
=IF(B3=B2,ROUND(D3-D2,2),"")

 

[Asquare]

Tetra201 Thank you for your time and help.