Global Variables

How Do I set global variables,

The variables are on a worksheet.
When macro "XX" runs it checks the variable, then runs.

When running "XX' three or four times right after another. Each time "XX" runs it check the worksheet. I think it would be faster to bring the variable into memory and use it every time "XX" runs.

Would this be faster or am I wasting my time writing the macro to use global variables.

Thanks, But how I do it?