You would need VBA for this, of course if it is as simple as in your example
with 2 cells and just the operand in one you can use

=CHOOSE(MATCH(B1,{"*","+","-","/"},0),A1*C1,A1+C1,A1-C1,A1/C1)

if not you can download Lauremt Longre's excellent add-in
it has a function called EVAL used as

=EVAL(CONCATENATE(A1,B1,C1))

it's here

http://longre.free.fr/english/

English description here

http://www.rhdatasolutions.com/morefunc/

Regards,

Peo Sjoblom

"Renny Bosch" wrote:

In trying to use Excel to help solve a mathematical puzzle, I would like to
calculate the result of applying the mathematical operator in one cell to
the numbers in two other cells.

Example: A1 contains 2, B1 contains +, C1 contains 3. In D1, create a
formula that will give the result of 2 + 3, i.e. 5.

I have tried (among many other attempts)
=VALUE(CONCATENATE(A1, B1, C1)), but it gives me a #VALUE! error.

What am I missing?