3 Month Average Using &OEP_CurMnth

Summary:

I'm trying to extend OOB functionality by creating a 3 month average driver. I'm working on a calc script to test functionality. I currently have the substitution variable OEP_CurMnth = Feb.

For some reason it is not jumping into the right if condition, and instead evaluates to the else condition. I can't figure out why its jumping into the elseif section. When it gets to the else condition it fails because the @XRANGE is invalid, as its looking at 2 months prior to Feb and it doesn't exist.

Content (please ensure you mask any confidential information):

Any idea why it is always jumping to the else condition and failing?