I'm tied up with something for the moment.

Storyline: What would you say when you are very busy with something and can't just put it aside even though your wife is calling you?
	Priscilla:	Rich, can you come downstairs for a minute right now?
	Richard:	I'm sorry I can't.  I'm tied up with something urgent at the moment.
	Priscilla:	Oh, are you on the stupid net again?  When are you going to get off?
	Richard:	Just a minute, Dear!  I'm looking at a new jewelry site.  I wanna make sure I get the right gift for your birthday, don't I?
	Priscilla:	Oh?  In that case, I'm sorry to bother you.  Take as much time as you need.
	Richard:	No problem.