Bui,
What exactly are you attempting to do? Capture a double click event. You can place your code or actions in the double click method such as populating a field or what have you. I use a grid most of time I want to show my users what's available and give them the option to either print or conduct some sort of action...

Here's a typical double click event:
If this.value = .t.
this.txtfield = .t.
perform your action
else
this.txtfield = .f.
perform your action
endif

HTH

Jeff