NEXTSIBLING in fix using Period dimension

Hello experts,

I have a question about NEXTSIBLING using in FIX.

I would like to see

FIX("FY23", @MEMBER(@NEXTSIBLING("ClosedMonth")):"Dec","E01")

Mycode...

ENDFIX

My period dimension is standard with native hierarchy:

YEartotal /// Q1 /// Jan /// Feb /// Mar /// Q2 ....

If closed month is Jan or Feb my fix working fine, but if ClosedMonth is Mar/Jun/Aug...is not working because machine choose Q1/Q2...

How can I fix this? I don't want to create additional variable called OpenMonth..

Regards