Field WdgNullValue, WdgOffValue and WdgOnValue
The value of a toggle button or menu item. Specifies the value of a toggle button or menu item in the OFF, ON, or NULL states.
A 256-character string
If the toggle object has no ValRule, then WdgOnValue is used to determine whether the object is set “on”. (The object is “on” only if its current value exactly matches the WdgOnValue.)
If “allow nulls” is off (AN = N), then a toggle button may never exist in the null state.
Menu items are not permitted to exist in the null state.