Modifier cell that contains both operator and value

[starchyfind]

I'm trying to incorporate a new feature into an already existing spreadsheet I maintain, but I'm having trouble finding the right functions and/or logic. Basically, I'm trying to give the user a column (in this case, B, in the table below), which will allow the value in Column C to be modified depending on the value and operator entered in Column B. I'd like this functionality to be limited to a single column (or single cell per row, as the case may be).

How can I make my existing formula work or what is a better method?

This is how I'd like the logic function, but it only works with the "*" operator:
[TABLE="class: grid, width: 500"]
<tbody>[TR]
[TD]
[/TD]
[TD]A[/TD]
[TD]B[/TD]
[TD]C[/TD]
[/TR]
[TR]
[TD]1[/TD]
[TD]=IF(SEARCH("~*",B2,1),C2*RIGHT(B2,1),IF(SEARCH("/",B2,1),C2/RIGHT(B2,1),IF(OR(B2<0,B2>0),SUM(C2,B2))))
[/TD]
[TD]5[/TD]
[TD]10[/TD]
[/TR]
[TR]
[TD]2[/TD]
[TD]=IF(SEARCH("~*",B3,1),C3*RIGHT(B3,1),IF(SEARCH("/",B3,1),C3/RIGHT(B3,1),IF(OR(B3<0,B3>0),SUM(C3,B3))))
[/TD]
[TD]-5[/TD]
[TD]10[/TD]
[/TR]
[TR]
[TD]3[/TD]
[TD]=IF(SEARCH("~*",B4,1),C4*RIGHT(B4,1),IF(SEARCH("/",B4,1),C4/RIGHT(B4,1),IF(OR(B4<0,B4>0),SUM(C4,B4))))
[/TD]
[TD]*5[/TD]
[TD]10[/TD]
[/TR]
[TR]
[TD]4[/TD]
[TD]=IF(SEARCH("~*",B5,1),C5*RIGHT(B5,1),IF(SEARCH("/",B5,1),C5/RIGHT(B5,1),IF(OR(B5<0,B5>0),SUM(C5,B5))))[/TD]
[TD]/5
[/TD]
[TD]10[/TD]
[/TR]
</tbody>[/TABLE]

Thanks.

 

[sijpie]

If you want to modify the value in C, depending on the value in B, then why is your formula in A?

 

[starchyfind]

If you want to modify the value in C, depending on the value in B, then why is your formula in A?

The value in C is reference to elsewhere in the spreadsheet, and wants to remain both unchanged and visible to the user. The value in A is the value in C multiplied by a referenced mark-up percentage. What I want to be able to do is affect the result of C*mark-up in column A by whatever is entered into column B. Hopefully that makes sense.

 

[sijpie]

OK, and these are only the mathematical operators +-/* ?

Formula in A14:

=IF(LEFT(B14,1)="+",RIGHT(B14,LEN(B14)-1)+C14,IF(LEFT(B14,1)="-",-RIGHT(B14,LEN(B14)-1)+C14,IF(LEFT(B14,1)="*",RIGHT(B14,LEN(B14)-1)*C14,IF(LEFT(B14,1)="/",C14/RIGHT(B14,LEN(B14)-1),ERROR.TYPE(#VALUE!)))))