Want to call jscript "confirm" box from VB.NET, but NOT from a but

[JT]

In looking around on the internet to find out how to use a "messagebox"-like
window on a webform, I have come across a few examples of how to do so from
the "onclick" event of a button. In my situation I am using a third party
treeview control that has a context menu on each node. If a user clicks on
one of the context menu options, I would like for a "confirm" box to pop up
and make sure that's what they wanted to do. I would be very grateful if
someone could explain to me how to do one of the following:
1) Cause one of these confirm boxes to pop up by calling it directly from
the context menu eventhandler in my serverside VB.NET code
2) Cause the "click" event on a button to fire from the same context menu
eventhandler in my serverside VB.NET code (the idea being that I could hide
one of these buttons I've seen that calls a "confirm" box, "click" it from my
code, and all the user would see is the "confirm" box popping up when they
click on the context menu)
I've tried everything I can find on either subject and I'm just plain stuck.

Thanks in advance for any advice,
JT