Synchronization to update only internals and not to touch active externals

I have a CSV sync which contains internal persons, I have also Externals in my One Idenity which should not be updated even if the matching rule matches.

I tried to create a rule in to Synchronization workflow:

isExternal = False or (IsExternal = true and Extidate < GetDate())

So it should update only non-externals and  also not-active Externals. But the "GetDate" -function is not working there? So how I can use the date in that rule?

I'm using version 8.0