Thanks for the suggestions.
In case anyone wants to know, I did not find a variable, but I did find a registry setting. Here's what I came up with to read the value.
(defun getreg ( / HKCU)
(vl-load-com)
(setq HKCU (strcat "HKEY_CURRENT_USER\\" (vlax-product-key))
HKCU (strcat HKCU
"\\Profiles\\"
(getvar 'cprofile)
"\\Dialogs\\Layertools\\"
)
)
(print (vl-registry-read HKCU "ISO_Vpfreeze"))
)
A value of 2 is "lock and fade". A value of 0 is "off".
Martin