Crystal Reports multiple record selection formula in C#

Message


     hello
I am newbie in crystal report .
I need some help regarding creating record selection formula 
Basically i am linking 2 tables and i want to generate report which is 
depend upon values given by user
here is my code:-

 string temp = "{source.receipt_no}like 'RD*'AND {source_master.name}='" +
 frmReport.source_name +
 "' AND {source.ayid}='" + frmReport.aca_yr_id + "'";   
 rptreport.RecordSelectionFormula = temp;

i am receiving error like 'This field is not known' 


its urgent....please help