Opening another browser window is not something you can do from server-side
code. Only the client can control the client. You have 2 questions here so
let me answer them individually.
1. How to call the click event of a button from the click event of another
button: This is accomplished by simply placing a call to the click event
handler of the second button in the first:
Sub Button1_Click() Handles Button1.Click
'Call the click event handler of button2
Button2_Click()
End Sub
Sub Button2_Click() Handles Button2.Click
'Button2's click event code here
End Sub
2. How to open a new browser window. As stated, only client-side code
(JavaScript) can do this, so you either have to embed a client-side script
and add a client-side event handler to a button
(onClick="window.open('fileToOpen')) or send this code to the client-side
control from the server side:
Page_Load()
Button2.Attributes.Add("onClick","window.open('fileToOpen')")
End Sub