ComboBox behavior

Hi,
I have an application in which the user can enter search data in a combo box and then click on the search button to initiate a search process. While the user is typing into the combo box, the combo box has to fetch some historical data from the Database. Due to this, as soon as the user types in something in the combo box, a progress cursor appears and keeps on blinking for a while(apparently the combo box is being loaded with historical data during this time)Till such time that the progress cursor blinks, if the user clicks on the Search button, the search process is not initiated and the application appears buggy. Looks like while the progress cursor is blinking, any key press operation won’t work, as there is some server processing occurring.
How can we overcome this issue ?

Thanks a lot for your help.
kavita