Re: Use a drop-down list to choose what kind of calculation to apply to certain cells

You might use this formula approach. Keep the original values in a hidden range or worksheet. This example uses column-P

=IF(A3="show original value",P3,P3/(1*MID(A3,MIN(SEARCH({0,1,2,3,4,5,6,7,8,9},A3&"0123456789")),LEN(A3)-MIN(SEARCH({0,1,2,3,4,5,6,7,8,9},A3&"0123456789"))+1)))

This assumes you only ever want to divide. If you are going to use other operators you will need a different solution.

If cell A1 is used as a drop down to select the math operator (add, subtract, multiply, divide),

The item list in column-I would be changed to =$A$1&" by 2", etc. (or use =$A$1&" by "&ROW(A2) and drag the formula down to automatically increment the number value).

The formula to calculate per the chosen operator would be

=EVALUATE(P3&LOOKUP(A1,{"Add","Divide","Multiply","Subtract"},{"+","/","*","-"})&1*MID(A3,MIN(SEARCH({0,1,2,3,4,5,6,7,8,9},A3&"0123456789")),LEN(A3)-MIN(SEARCH({0,1,2,3,4,5,6,7,8,9},A3&"0123456789"))+1))

It would simply the formula if you just used A1 to select the operator type and let the A3 drop down be a list of numbers only. Then we could just use:

=IF(A3="show original value",P3,P3/A3)