Reloading select without reloading the page

Hi,

I have a quick question since i am a newbee in this
I am adding dynamically rows in a table using DHTML.
The thing is one row is composed by 3 select directly connected to an
mysql database. I choose the first select so the option on the second
appear an so on.
But how can i do it on multiple row adding with DHTML ?

I don't know if i am understandable.

Thanks for your help.

Pierre