## open dialog

function callDialogFunction(){
var args = {_in:{someInArgument:value}, _out:null};
window.openDialog(url,
"_blank",
"chrome,modal,resizable=no,centerscreen,width=400,height=280", args);
var user = args._out.userName;
var password = args._out.password;
if(!canLogin(user,password)){
   callDialogFunction();
}
}

## inside dialog, on accept function

window.arguments[0]._out = {userName:user, password:password};