Filter by field functionality on display method

Override the context method of form control of display method. Following is the example of filtering customer name.

public void context()
{
    // super();
   Int      selectedMenu;
   real     test;
   formRun  fr;
   Args     ag;
   Name     strText;
   str          custAcc;
   CustTable    custTable;
   Container    cust;
     FormStringControl   fsc;
   PopupMenu    menu    =   new PopupMenu(element.hWnd());
   int a = menu.insertItem('Filter by field');
   int b = menu.insertItem('Filter by selection');
   int c = menu.insertItem('Remove filter');
   selectedMenu = menu.draw();
   switch(selectedMenu)
   {
        case -1 :
        break;
        case a :
        ag =  new args('SysformSearch');
        fr = new formrun(ag);
        fr.init();
        fsc = fr.design().controlName('FindEdit');
        fsc.text(customerName.ValueStr());//customerName is display control name
        fr.run();
        fr.wait();
       strText = fsc.valueStr();
       while select custTable where custTable.Name like strText
        {
            cust += custTable.AccountNum;
        }
        custAcc = con2str(cust);//custTable.AccountNum;
         if(fr.closesOk())
          AVI_ServiceOrderTable_ds.filter(fieldNum(AVI_ServiceOrderTable,CustAccount),custAcc);
         break;
        case b:
            strText = customerName.valueStr();
            select custTable where custTable.Name == strText;
             AVI_ServiceOrderTable_ds.filter(fieldNum(AVI_ServiceOrderTable,CustAccount),custTable.AccountNum);
            break;
        case c:
        AVI_ServiceOrderTable_ds.removeFilter();
         break;
   }
}