Hi
Is it linked subreport or unlinked ,you need to if Linked you need to link the main report with subreport using the change subreport links once done in avialable fields move the field in Field(s) to link once done a subreport parameter field to use is created on left below.
Uncheck Select Data in subreport based on field then go to subreport and in record selection formula of subreport check for (?PM-Field name} = ur table.fieldname
Cheers
Rahul