Excel SUM and SUBTOTAL in a filtered list

[MYUSERNAMEIS]

Hello,
Please can you help me with working out a formula.

I want a formula that will total the unique supplier postage costs even if the data has been filtered by another column (In the example - COLUMN D)
i have tried various different formula found on here but none of them seem to do what i need. (combinations of COUNTIF, SUM, SUBTOTAL, FREQUENCY, MATCH)

1	A	B	C	D
2	Item	Supplier	Postage
3	scissors	Company A	£1.00
4	tables	Company B	£15.00	hidden
5	paper	Company B	£15.00
6	pens	Company A	£1.00
7	tape	Company C	£0.50
8	pencils	Company D	£0.00
9
10			£16.50

<tbody>
</tbody>

If the formula did what I wanted it to do the result in C:10 would be £16.50
There are many more rows and columns with other formulas to take into account. It also has to be a result that is just visible, without the end user having to do anything - so i don't think a pivot table.

I am also a complete novice at Excel so would also appreciate if you could explain what the different bits in the formula actually do.
if anybody could help or point me in the right direction i would be so greatful!
myusernameis

 

[Domenic]

Try the following formula, which needs to be confirmed with CONTROL+SHIFT+ENTER...

=SUM(IF(FREQUENCY(IF(SUBTOTAL(3,OFFSET(C3:C8,ROW(C3:C8)-ROW(C3),0,1))>0,MATCH(C3:C8,C3:C8,0)),ROW(C3:C8)-ROW(C3)+1)>0,D3:D8))

Also, to take into account both filtered and manually hidden rows, replace 3 in red with 103.

Hope this helps!

 

[MYUSERNAMEIS]

Thank you so much Domenic.
This does exactly what I want it to. I've been wrestling with this for weeks hoping to eventually stumble on the correct combination - I was nowhere near this - again thank you so much!

 

[Domenic]

You're very welcome. Glad I could help.

Cheers!