Inserts a separator into the pop-up menu at the specified location.
- [in] iInsertAt
The zero-based index of the position where this method will insert the separator.
The zero-based index of the position where the separator was inserted. -1 if this method fails.
A value of -1 for iInsertAt means this method will add the separator to the end of the pop-up menu.
This method fails if iInsertAt is an invalid value.