How can I filter calendar table by field ClipEnd?

[bing yu]

I am trying to restrict the results of a search by ClipEnd.

MAPINAMEIDInt mni;

mni = new MAPINAMEIDInt(new Guid("00062002-0000-0000-C000-000000000046"), 0x8236, TagTypes.TypeSysTime);

Tags clipEndTag = MAPI33.Helpers.Property.Tag(TagTypes.TypeSysTime, (ushort)mni.id);

calendarTable.SetColumns(new Tags[] { Tags.ptagLongtermEntryId, clipEndTag }, IMAPITable.FLAGS.Default);

MAPI33.MapiRestrictions.Compare c1 = new MAPI33.MapiRestrictions.Compare(clipEndTag, MAPI33.MapiRestrictions.Compare.TYPES.GreaterOrEqual, Value.Create(clipEndTag, DateTime.Now));
returnValue = calendarTable.Restrict(c1, IMAPITable.FLAGS.TblBatch);

But it always return null. Can anyone point me in the right direction?

Thanks

Bing