Use MTEXTED to prefix your wordpad text editor with :lisped# as in:
:lisped#C:\Program Files\Windows NT\Accessories\wordpad.exe
If the mtext entity has less than 32 characters it will pop up in a dialog box editor just like single line text, more than 32 will pop to the editor.
(defun c:mxtxtg ()
(if (= (strcase (getvar "mtexted")) "INTERNAL")
(setvar "mtexted" ":lisped#C:/WINNT/system32/notepad.exe")
(setvar "mtexted" "INTERNAL")
)
)