Here's a list of the types of things you can do with client-side scripting without a round trip to the server:

• access the value of a cell
• set the value of a cell
• raise an event when a specific value is entered into a cell
• test if the user has changed the values in the Spread cells (no matter what cell)
• determine if the active cell is in edit mode
• warn the user if they fail to fill in a particular cell and allow them to go back and fill it in or leave it blank and continue
• find the column of the active cell and change the background color of that column’s header

To see some samples, refer to Some Simple Uses of Client Scripting.