Knowing what to actually search for in this case is difficult if you don't know any correct keywords to use as CLEAR/DELETE/BLANK/ADSI are not very helpful keywords for this.

Here are some links from a couple years ago where it came up.

http://www.kixtart.org/ubbthreads/showth...page=0&vc=1

http://www.kixtart.org/ubbthreads/showth...page=0&vc=1

Modifying Attributes with ADSI


ADS_PROPERTY_OPERATION_ENUM