>I use 'Execscript' to run a code which is stored in a table . But an error appeared :'THISFORM can only be used within a method'


Agnes,

The error correctly indicates that you cannot apply THISFORM unless you are running inside the form (as a container).
You can always use with _SCREEN.ActiveForm to get a reference to whichever form is active from the Forms collection.

A better way if you want to run that program from anywhere outside a form would be to take a reference to the ActiveForm and then use that to refer to the form's PEMs.

ExecSript() is very powerful but very dangerous as anybody could change the program inside your Memo field and make a malicious entry. Be sure to either have the code encrypted or somehow validate that it has not been changed by unauthorised hands.