Help On Ajax Modal Popup

Hi all,

   Please i need help on how to use the Modal Popup. What i want to achieve is this,

•   I have a textbox and a button for Searching Purposes
• When the user types the search parameter and clicks the search button, the Modal Popup should come up and prevent the user from clicking anything on the Page Until the Search returns a message.

Please i will appreciate any help on this.

Cheers,