Multiplying 2 Cells if another cell meets criteria

[tho_kva2]

Hi,
I want the cell A to be multiplied with cell B when cell C shows 1 (eg 1.46*1=1.46), but when cell C shows zero I want it to show -B (-1). Is there any easy way to make this happen?

English isn't my first language, so i hope this made any sense

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[JohnTopley]

=IF(C1=1,A1*B1,-B1) assuming C1 is either 1 or 0

or

=IF(C1,A1*B1,-B1)

[tho_kva2]

Thanks for a fast answer, probably bad explaining but I want that if C is 0 then ill get what stand at B as a negative number. If I use your forumla i'll get 0 when C is 0. I want the negative number of B.
This is accounting/investing, when there is 1 at C ill have A(return) on B(invested). While when there is 0 at C ill have no return on the investment and will have -B(Invested) In my example -1.

[JohnTopley]

No you will not: try it

You cannot put the formula in C (circular reference)

in D1 ..... =IF(C1=1,A1*B1,-B1)

A1=3
B1=2
C1=1
D1=6


C1=0
D1=-2

[tho_kva2]

Sorry for the confusion.. I must have miss typed or something, thanks for the help and clarification!