IFTHEN function on a formula column in Narrative Reporting

Summary

IFTHEN function on a formula column in Narrative Reporting

Content

Hello,

I am trying to use IFTHEN function on a formula column. I need my column to have value based on Period member.

If Period = 'Mar', Col[B],Col[A] - If Col B has period Mar, display col B values in formula column else display col A values.

IFTHEN(Col[B]='Mar',[B],[A])

But, Period is not considered is in the IFTHEN function.

Any thoughts on how this can be achieved.

Thanks in advance.