How to restrict internal customers to access a pop up page

[jayamalini]

I have a page which has a pop up page. the pop up page should be visible only for external customers. when the main page loads, internal customers within an ip range should not get the pop up page, I have a code

Dim clientIP As String = Request.ServerVariables("REMOTE_ADDR").ToString



If InStr(clientIP, "120.254") = False And _
InStr(clientIP, "080.91") = False And _
InStr(clientIP, "090.256") = False And _
bodypopup.Attributes.Add("onLoad", "popup('http://www.website.com/popup.html', 'popup');")


but it doesn't filter my ip s which are starting from 120.154, how can i filter these IPs?do I need to use some thing else than Instr?