Kiyomi,

   I don't quite understand your question, but if you want to display a
modal dialog to the client (triggered from the server-side code), then the
best way to go about this is to create a simple JavaScript function on a
global JS file that all your forms include.  Then call this function form
your server side and pass in the crucial parameters like URL to the dialog
form, width, and height.  Sample code below and I hope this helps.

- Rashad Rivera <spam@omegusprime.com>
 www.omegusprime.com

=====
myForm.cs code

...
private void Page_Load(object sender, System.EventArgs e) {

   ...

   if (isTimeToShowDialog) {
       this.RegisterStartupScript("someUniqueName",
"myJSDialogMethod('/theDialogForm.aspx', 450, 300);");
   }
   ...
}

=========
client side: global.js
...
function myJSDialogMethod(url, width, height) {
   return
window.showModelessDialog(url,null,'dialogHeight:'+height+'px;dialogWidth:'+width+'px;edge:Raised;center:Yes;help:No;resizable:No;status:No;');
}

Thank you for your kind advice.
I managed to make my popup work, using RegisterStartupScript as follows.
Now, I wish to retrieve user's response (OK or Cancel) and depending on
the response, I wish to continue different processes.  Would you please
advice me how I can do this ?

Thank you very much.

My HTML page

function doConfirm(msg) {
var x=showModalDialog('Confirm.htm', msg, 'status:no;resizable:yes');
}

My VB code behind page

Function CheckRules()

Dim msg as String
msg = ?An error is detected.  Do you want to continue processing ? ?

If (Not Me.IsStartupScriptRegistered("Startup")) Then
  Me.RegisterStartupScript("Startup", "<script>doConfirm('" & msg &
"');</script>")
End If

----- After running doConfirm(msg) This is what I wish to do --------

If doConfirm(msg) returns True (i.e., user clicks OK button)
    Continue processing below
Else (i.e., user clicks Cancel button)
    Return False
    Exit Function
End if

----- Continue processing

Return True

End Function