Programatically navigate to url

[Monty]

Hi, I need to open a page filtered to a certain employee. I plan to do this
by programmatically opening the page. How do I do this?
I tried the following...

If GriEmployee.SelectedIndex = 1 then
NavigateURL = "~/PatientEntry.aspx"
End if 'something like this... but it doesn't work.

Thank you, Mark