Change a Polygonal VPort Rectangular?

I've sometimes had the need to take a viewport that was previously polygonal
and change it to rectangular. Now I know that I can use the grips to move
the vertices--but I'd like to get rid of the associated pline.

If I remove the 340 dotted pair from the vport list, will that safely
disassociate the polyline from the vport? Of course I assume that I'd have
to delete the pline myself.

Also, what about going the other way. If I want to change from rectangular
(no pline associated) to polygonal. Will this work?

(setq PLEName (cdr (entsel)))
(entmod (append VPort (list (cons 340 PLEName))))

I'm using Ac2k4.

TIA

 

You can't entmod a viewport, and there's no ActiveX method I can find to modify
its clipping.
So to get rid of the clip:
(if (setq clip (cdr (assoc 340 (entget vpentity))))
(command "_.VPCLIP" clip "_D")
)

To add a clip by points:
(command "_.VPCLIP" vpentity "_P")
(mapcar 'command ptlist)
(command "_C")

To add a clip by another entity:
(command "_.VPCLIP" vpentity another-ename)

Unfortunately, the viewport's layout must be current.

 

Thanks John. I'll give that a try.