Anny, this is a question that comes up frequently enough that I've actually linked this thread in to the FAQ.
I think the short answer is that as far as I know, there is not a way to do this. I've come across a number of times when I've wanted to do this, and I've ended up rewriting the code a little. Usually, I've found other ways of doing the same thing.
One thing I've done, for example, is to manually create my own multirow.
Anyone else know a way to do this? Dave?