ATTRS rule function returning invalid expression

[lynnsong986]

Hello,

I have this rule that gave me errors:

['BillingMonth']=N:ATTRS('SM_Projects',!SM_Projects,'BillingMonth');

BillingMonth is a string attribute in the format of "YYYY-MM". can someone please let me know what I did wrong here?

[ascheevel]

is ['Billing Month'] a string measure in your cube? If so, you wrote an N: level rule, try S: instead.

[lynnsong986]

thanks so much, exactly where I did wrong!!