Avoid users to select itself as the next step assignee

Hi,

Is there any way to avoid a user to select itself as the assignee for the next step (To field)? Some users are in more than one group, and we would like to exclude this user from the assignee list.

I think that if we had a DE with the login or the name of the user who accepted the task we would be able to create a filter based on it, but i don't think that this kind of DEs exists. Does any one know?

Thanks a lot,