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?