Passing Global Variable Value BACK from System Command?

Is there a way to pass a value BACK to a Global Variable in Process Flow?
Example: Start declares var1="ONE"
Then I execute System Command (Unix script) testvar.sh
In my Unix script I accept the variable:
variable1=$1
and then change it:
variable1="TWO" and 'echo' confirms the change.

However, when I return to process flow, var1 continues to
retain the value "ONE".

(Obviously, "variable1" does not occupy the same location as the passed, global variable, "var1".)
Is there a way to pass a value BACK? Using var1 or perhaps some OTHER means?
Thanks!