Killing a Process

The code below opens up an another process which displays a simple pdf help file. When my main app closes I would like to force close (kill I think it is called) the Help screen. I have played around with the OS & Phone libraries and think if I could somehow get the PID number that I could get it to work with maybe Phone.Shell("Kill".... Can anyone show me the code to do this exercise.

Sub mnuHelp_Click
Dim iLook As Intent

iLook.Initialize(iLook.ACTION_VIEW, "file://" & File.Combine(File.DirRootExternal, "/BillTest/Myhelp.pdf"))
iLook.SetType("application/pdf")
Try
StartActivity(iLook)
bHelp = True
Catch
ToastMessageShow("Cannot open file.", True)
End Try
End Sub