Modeling changing facial expressions?

[Josh]

Hi all

I need my avatar to express several emotions that should be changing fluently. For example I want the avatar to smile and then change to frown.

How can I do this? I guess using some sort of morphing? I know that I can attach a head to my avatar, so I could create 2 heads (one smiling and one frowning) and then morph from one to the other, right?

Could anyone please give me a hint into the right direction for doing this? :-)
Best would be if I could morph also to a certain degree, let's say 50%, so the facial expression would be neutral then. Is this possible?

Thanks a lot :-)
Josh