pfnCompare (PFNCOMPARE)
A comparison function is used when the object is doing its own Include Page filtering (in the Settings notebook).
For example, if a string details field exists, the field could be set to pfnCompare = StringCompare, where StringCompare is defined as:
LONG StringCompare(PSZ str1, PZS str2)
This field can be NULL unless ownerdraw is used.