How to modify a formula using a value in one column that then impacts on two others

Hey everyone! I'm new here but (I think) better than the average normal person at excel. Macros still confuse me, and I'm not sure what is the best solution for this problem. I'm trying to write a formula that will run different calculations of a cell range (only one number in each cell) depending on what is entered in a main cell. There are about 5 different formulas that I'm looking to input. The general idea is this:

Cell A - Text Entry (which determines which of the 5 formulas are run - these formulas will take the number inputs in cells B,C)
Cell B - Number entry
Cell C - Second number entry
Cell D - Output of Formula (determined by Cell A)

I've run several nested IF functions to test this, but I keep running into issues because I want the output to vary based on the text entry of Cell A.