Ajax and Adsense


I've got a question on implementing Adsense with a dynamic content
which uses ajax to change the content.
So, let's say I have two DIVs that I put on the same page, the first
DIV contains the dynamic content which is updated using Ajax, the
second DIV is where I put my Adsense code.

My question is, how can I tell or maybe more precisely, how can the
Adsense code knows that the content has changed, hence adjusting the
ads accordingly ?
Anybody got some tips and tricks on this subject ?

Thanks a lot !