I usually put the membernames in quotes, so "Feb":"Dec".
In our applications we use a shortcut, we have a FcstStartMonth variable. Just to come around this problem.
Maybe you have also a CurrMonth which you could use with @NEXT.
I never saw other solutions like @SUBSTRING but maybe with Quotes it recognizes it as a member.
Glad to hear from you, I hope you are doing well. I've previously seen something like this using concatenate (see code below).....
VarPart = @member(@concatenate(@name(@parent(@currmbr("Company"))),"_Input"))
IF(VarPart+1<>1) /* i.e. not missing or zero */
I was hoping substring would work. I think I'll use CurrMonth with @NEXT.
Many thanks for your help