Crystal report problem

Question

Hello, I am developing Desktop application(for Hospital) in C# Frontend:Visual studio 2010 Backend :SQL server 2008

I am showing prescription through crystal report(by dataset programically)I am clearing Dataset everytime before giving reference to crystal report. I have given medicine details in details section.(medicine type,name,frequency & quantity) But, I getting previous records along with lattest ones in crystal report.Also,whole series of previous & lattest records repeating. I want to show only lattest records i.e. (medicines given for patient's current visit on Prescriotion). Please help me.