How to empty an attribute in MV before export?

Hi,

sry for the noob question: I'm looking for a possibility to empty an attribute before i Export it?

I have 2 Active Directory MA. One imports objects and attributes to the MV and the other exports the attributes to an other Active Directory.

Sometimes i need the possibility to empty an attribute before exporting it without to delete the attribute flow.

If i try to use a constant then i can't set it to an empty value. Is there any (easy) possibility to empty the attribute so it is set to <not set> in the target active Directory? (for every Attribute type...e.g. DN, string, boolean, ...)

Thank you!