How to use button in gridview in asp.net using C3

   In database records as follows   Room   Course   11        EFA 12        RFA   13        MFA   14         ROC     Gridview as follows    Room Course   11 Button1   12 Button2   13 Button3 14 Button4   for each room i place the Button inside the gridview, when i click the each Button i want to pop up the dropdownlist,in that dropdownlist values are to be retireved from the database. for each room course are assigned that i mentioned as above.   so when i click the button display the dropdownlist,select the course that course to be postion into the partiuclar room in the gridview.   for that how can i do using csharp.  

 Narasiman