Hi,
I am trying to delete  CustomDocumentProperties but by using following code:
object[] TheArgs = new object[] { PropName, false, 
MsoDocProperties.msoPropertyTypeString, PropValue };
TypeOfAllCustomProps.InvokeMember("Delete", BindingFlags.Default | 
BindingFlags.InvokeMethod, null, AllCustomProps, TheArgs);
I get this error: 
System.Runtime.InteropSerive.COMException (0X80020006): Unknown name. 
(Exception from HRESULT: .....
at Sytem.RuntimeType.InvokeDispMethod(string name, BindingFlags 
invokeAttr,....
somewhere i saw that you can use CustomDocumentProperties.Remove.
But it is not right. 
thank you for your help