[Outlook Automation]Adding user property to contact item

[Marcel Stör]

Hi all,

I'm trying to add a user property to an Outlook contact item.
VisualStudio tells me that the method signature was like this:
UserProperties.Add(string Name,Outlook.OlUserPropertyType Type, object
AddToFolderFields, object DisplayFormat)

So, what I do is:
oMyItem.UserProperties.Add("myProperty",Outlook.Ol UserPropertyType.olYesNo,
true, XXX???XXX);

How can I determin the display format?
All I've found on MSDN was a MS Outlook VBA reference. There it says:
"DisplayFormat Optional Long. The index format of the specified
OlUserPropertyType constant."

My next question would then be how to determin the index format of
Outlook.OlUserPropertyType.olYesNo.

Any help is greatly appreciated.
Marcel