how to identify which button was clicked

Question

Assume that I want to create 100 buttons layed out in a table of 10x10 and 1 Submit Button.User has to select some of the button in that table.After he click submit Button.In this Submit button click event I have to change the back-ground color of all buttons which are selected by the user. I have tried with Arrays,I have created an array which is button type And i have added the button when it is selected by the user to the array. When i have used that array elements in the submit button event,Iam unable change the back-ground color of that buttons. What is the best solution for this? I want solution in ASP.Net 1.0