Run Popup Window/Dialog after Server Code is run

Hi,

I am having problems with the popup dialog and understanding how it works.

The process in my page goes as follows:
- The user completes filling all the textboxes, radiobuttons, etc
- User clicks on the submit button
- Validation happens on the Client Side
- After Validation is done, it runs the Server Code (had to be done this way because I am running some database and functions that can't be done under javascript)
- At the end of the function that is ran in the Server Code, the user should then be shown a popup window or dialog which will be telling it to add some data.

Now the problem I am having is creating this popup dialog, I have looked at different places in "how to" but I still dont get it, using DIV seems to be working for everyone but I don't see anyone running it from a Button; only from a href. and as for what I can see after a postback, also the data that is in the original window will be used in this popup window (kind of sending data back and forwards but only obtaining the data so then it can be finally be sent to the database, so it needs the data in i.e the textboxes).

Please any help with this would mean a lot!
I can give more information if needed.