CouldDialog
CouldDialog Make a dialog and related resources un purgeable
#include <Dialogs.h> Dialog Manager
void CouldDialog(dlgRsrcID );
short dlgRsrcID ; resource ID of a dialog (type 'DLOG')
CouldDialog is needed when you expect that a disk containing dialog
resources may be removed. It reads 'DLOG', 'DITL', 'WDEF', 'PICT','CNTL',
'dctb', 'ictb' and related resources into memory along with the color table
template (if not already there) and tags them as un purgeable.
CouldDialog is not supported under System 7. You can call it but no
operation will be performed.
dlgRsrcID is the resource ID of the 'DLOG' resource you want held in memory.
Returns: none

Notes: CouldDialog is a quick way to insure that a dialog and all its related
resources (with the exception of the 'FONT' or 'FOND' resources indicated in
the color item list) will not be purged. The alternative is a series of a
(possibly) large number of SetResAttrs calls, walking around an extended
tree of resources.
Exception: If the dialog uses a font other than the system font (see
SetDAFont), that font might get purged anyway. You may wish to lock it
Use FreeDialog to undo the effect of this call.