Window
parameter selection.
Identifies the window parameters that are to be set or queried. Valid values
for the slider control are:
WPM_CBCTLDATA
Window control data length.
WPM_CTLDATA
The
flags in the status field are cleared as each item is processed.
If the call is successful, the status field is 0. If any item has
not been processed, the flag for that item is still set.