HELP!!!-Excell-like web-page (client&Server side)

i need HELP. <br>i have to make an excell-like small datasheet in a page.<br>there are 2 tables , and a summary table below.<br>when the user change a single value (in any cell) , the summary table and<br>the sum column at the same row , automaticly updates. <br>so far , so good , i can do all of that at the client side (using javascript) .<br>i also dont have any other choice than putting it as a client-side proccessing cause <b>the summary updates must occure as the user change a single value. i cant (and my boss dont want to) wait for a - postBack update every time a cell change </b><br>(it has to be like excell's cells formulas , the chage occur in place).<br><br>thats y i cant use the regular DataGrid comes with ASP.NET, also , i won't put 500 TEXT inputs (in each cell) , when the user click a cell i will place a text INPUT in that cell , thats y i need client-side proccessing.<br><br><br><br>the problem is , how can i send all of the data to the CodeBehind of that page? (i don't want to do 500+ hidden INPUTS ) , all of the data that will be placed is client-side generated , not a server-control generated.<br>how can i transfer that data to the server? (i dont think that attaching it as part of the url's GET section will be a good idea...<br><br><br><br>dont be afraid to come up with complex/usefull ideas , i am a newbie to asp.net specificly . i have been programming for 10 years (c/c++ / w32 and low-level) , so i m not afraid of good ideas , just be specific please. <br><b>