A VBA question, how do I?

In Excel using VBA I can write a macro that (conceptually) looks like this:

Sub MyThing()
… let MyVariable = something
… do some stuff with MyVariable
End Sub

What do I do different to pass a variable into MyThing and use it? I have a big chunk of code but I need to use it 10 times with 10 sets of variables. The only way I know how is to copy it 10 times and edit the variables. Then the code is to big to run.

I have to think this is a pretty basic question but it would sure helpme in my understanding. Please be complete!