>I get the error "Dblclick is read only" at run time when the statement below is encountered:
>thisform.mygrid.column1.text1.dblclick = 'thisform.command3.click()'

Right, you can't do that.

>Setting the dblclick event at design time works fine but is impractical because my grid columns need to be defined and displayed based on operator input.

Check out the Faq "Adding event code to grid controls at runtime" or something like that in the files section here.