I think it is not possible, if you are loading expressions from text file using $(Include) and variables then you can find and replace in a single shot.
Your text should consists of expressions like below
SET vExpression1 = Sum(Measure1);
SET vExpression2 = Count(DISTINCT ID);
And in Qlikview script you have to include this text file like below
Now in chart you simply use
Hope this helps you.