You can use the
code:
OnWindowIdEvent_CtrlClicked(pPlusWnd, sControlId){
//pPlusWnd is the Plus! object for the window
//sControlId is the Id of the control that is clicked
//To get the text use the following :
var sText = pPlusWnd.GetControlText('myTextBox');
}
To store it in the registry take a look at this page I made.
http://mattyg.ca/geshi/registry.php