IBP Disaggregation expression Attribut value

Hello,

I want consider an attribut value in my disaggregation expression.

So I want, that only the disaggregation works when the plm_status is "RL" So I try follow expressions

IF("PLMSTATUS"=´RL´,"ZWERTESAISONALYEAR2MONTH2",NULL)

IF("PLMSTATUS"="RL","ZWERTESAISONALYEAR2MONTH2",NULL)

IF("PLMSTATUS=`RL`,"ZWERTESAISONALYEAR2MONTH2",NULL)

in all options, the system interpreted "RL" as an attribut and not as attribut value. So the error message is, that the RL Attribut is not in the planning level

How can I consider attribut values in the disaggregation expression

Thanks in advance

Oliver