>...how to code the valid method so it won't allow them to leave the grid line.
Hi Douglas;

Each textbox control in its respective columns, should have something as:

procedure column1.text1.valid
return thisform.myvalid
endproc

procedure columnN.text1.valid
return thisform.myvalid
endproc

procedure thisform.myvalid
if  <cond1> && your cond. here
else
    return .f.
endif
return .t.

HTH

Claudio