Problem: adding an external domain

Hi guys,

I need help with my domain.
I want to use domain alexstoimenov.in.rs
My bplaced subdomain is stoimenov.bplaced.net

How should I configure my domain?

When I put alexstoimenov.in.rs in Domain field in bplaced "add an external domain section"
I get the message: The given domain is invalid! (it is red colored on the picture, see below).

What is wrong?
Please help.

[attachment=1]ScreenHunter_01 Jun. 27 13.03.gif[/attachment]
[attachment=0]ScreenHunter_02 Jun. 27 13.04.gif[/attachment]

plz wait for miro ( hoster)

i think the in.rs is the problem :S, maybe bplaced doesnt allow it yet