show sum of value till specific month and for specific class

[Mkh13646]

Hi everyone, 

I would like to show the sum of project progress which their activities class is "develop"  till the specific month ([MRS_PRJ_PROG.CURMONTH]) in my cell of a table, I write this code but it doesn't work, I appreciate  if anyone can help me to make this work

If(Valuelist('Lastmonth','Frombegin')='Frombegin', If(FMONTH <=[MRS_PRJ_PROG.CURMONTH],Sum({<TYPE_ = {"DEVELOP"}>}[MRS_PRJ_PROG.PROG_]))