You could try the GetTag() method. But this method returns the fully qualified tag which contains all of the ancestor's of the object, as in [from the online help example for the GetTag() method]:
Therefore to use this technique you will need to process the string returned by GetTag() to strip just the object's class [assuming in your case that this is not just CustomWin--you are going to have to experiement]. To post process this string I have attached two functions I wrote called StripBefore() and StripAfter(), which could be used to strip the "Checkbox" class from the above string.
Review the comments for these functions for usage in the attachment. [This file was uploaded as a Silk *.inc file, and hopefully can be saved with that extension to preserve its file format for Silk]
Hope this helps.
[This message has been edited by Terry Horwath (edited 11-23-2000).]
A subtle correction to John's post indicating that class mappings are located in partner.ini--that is true if you are not using an Option Set to define options for the application under test. If you are using an Option Set then the class mappings are stored in that *.opt file and not partner.ini.