TextChanged Event - Call WebService Without Page Refresh

I would like to perform some validation on an entry into a text box in the TextChanged event without causing the entire page to refresh.  For example, if a user enters an account number into a textbox, I would like to call a webservice that would validate whether or not the account number is an accurate account number.  If the account number is not valid, I would like to display a message in a label on the page.  This is being used within the context of a create user wizard, I would like to validate the account number and give the user a chance to correct it before they click the "create account" button.  Is this possible?