Variable in a variable name

I feel like this is such a simple question it’s surely been answered somewhere before, but I can’t find anything on google or the forum search that can help me.

I have several variables. To make it simple lets say they are named “VariableA” “VariableB” and “VariableC”.

They are each integers and I need to add 1 to each depending on what variable I am sent. So if I am sent, for instance, an “A” I need VariableA to increase by 1.

I’d really like to avoid a switch statement if possible.

I tried:

this[“Variable”+varLetter]++; //where varLetter is a string holding either “A” “B” or “C”

But that didn’t work.

Then I tried

this[“Variable”+String(varLetter)]++; //after finding a forum post on another forum that suggested this

But that didn’t work either.

I know I’m missing some fundamental concept I just can’t grasp! What’s the right syntax?