Map Network Drive By Group Membership

I seem to have a problem mapping a drive based on AD Group Membership. I want the script to map a drive if you are a member of a certain AD Group. If you are not a memeber I want it to display a message saying you are not a member of a that group. However I am a member of the group specified in my script but it returns an error saying not a member of the group. What have I done wrong?

'==========================================================================
'
' VBScript Source File -- Created with SAPIEN Technologies PrimalScript 3.1
'
' NAME: Kirk Marty
'
' AUTHOR: martyk , GTS
' DATE : 5/17/2005
'
' COMMENT:
'
'==========================================================================

'Mapping Network Drives According to User Domain

Set objNetwork = WScript.CreateObject("WScript.Network")
strUserDomain = objNetwork.UserDomain

If strUserDomain = "Domain Admins" Then
objNetwork.MapNetworkDrive "R:", "\\SPNAS1\Install", True
Else
WScript.Echo "User " & objNetwork.UserName & _
"not in Domain Admins R: will not be mapped."
End If

The UserDomain returns the domain from which the user logs on, not the group (or list of security groups) the user belongs to. To map a drive based on group membership, you can use the following function I wrote:

Function isMemberOf(group)
Dim user, found, temp
found = False
Set user = GetObject("WinNT://" & CreateObject("WScript.Network").UserDomain & "/" & CreateObject("WScript.Network").UserName & ",user")
For Each temp In user.Groups
WScript.Echo temp.name
If UCase(temp.Name) = UCase(group) Then
found = True
Exit For
End If
Next
isMemberOf = found
End Function

Then you can do the following.

If isMemberOF("Domain Admins") Then
objNetwork.MapNetworkDrive "R:", "\\SPNAS1\Install", True
Else
WScript.Echo "User " & objNetwork.UserName & "not in Domain Admins R: will not be mapped."
End If

Thanks Token. However I do get an error on Line (18,1)

Here is the error C:\scripts\test\ctxmap.vbs(18, 1) Microsoft VBScript runtime error: Object required: 'objNetwork'

This is line 18 and I do not see a problem with the syntax?
objNetwork.MapNetworkDrive "R:", "\\SPNAS1\Install", True

Any advice?

Actually I fixed it. Thanks again though Token I am much obliged...

No problem :)