An update is available for ISA Server 2006 integrated NLB that lets you add virtual IP addresses that are outside the subnet of the dedicated IP address

Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
Const SE_VPS_NAME = "AdditionalVIPsAndMask"
Const SE_VPS_VALUE = "<additionVIP1>/<subnetMask1>; <additionVIP2>/<subnetMask2>;"

' To run: cscript confignlbAdditionalVips.vbs /Network:External
' use the network name as appropriate.
' You must remove comment marks on the correct line to add or remove the VPS.

Sub NLBConfiguration()

    ' Create the root obect.
    Dim root  ' The FPCLib.FPC root object
    Set root = CreateObject("FPC.Root")

    'Declare the other objects needed.
    Dim array         ' An FPCArray object
    Dim NetworkConfig ' An FPCNetworkConfiguration object

    ' Get references to the array object
    ' and the protocols collection.
    Set array = root.GetContainingArray

    On Error Resume Next
    Set NetworkConfig = array.NetworkConfiguration
    CheckError

    Dim Networks ' FPCNetworks
    Set Networks = NetworkConfig.Networks

    Dim Network         ' FPCNetwork
    Set Network = Networks(WScript.Arguments.Named("Network"))
    If Err.Number <> 0 Then
        Wscript.Echo "Cannot find network, error- " &  Hex(Err.Number) & " " & Err.Description
        Err.Clear
        WScript.Quit(1)
    End If

    Dim VendorSets  ' An FPCVendorParametersSets collection
    Dim VendorSet   ' An FPCVendorParametersSet object

    Set VendorSets = Network.VendorParametersSets
    CheckError

    On Error Resume Next
    Set VendorSet = VendorSets.Item( SE_VPS_GUID )

    If Err.Number <> 0 Then
        Err.Clear

        ' Add the item
        Set VendorSet = VendorSets.Add( SE_VPS_GUID )
        CheckError
        WScript.Echo "New VendorSet added... " & VendorSet.Name

    Else
        WScript.Echo "Existing VendorSet found... value- " &  VendorSet.Value(SE_VPS_NAME)
    End If

    Err.Clear

'  Remove the comment mark from the following line to set VIPs. Make sure that there are no additional
'  VIPs defined in the UI.
'
'    VendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUE

'  Remove the comment mark from the following line to delete the VPS.
'
'    VendorSet.RemoveValue(SE_VPS_NAME)

    If Err.Number <> 0 Then
        CheckError
    End If

    Networks.Save false, true
    WScript.Echo "Done saving..."

End Sub

Sub CheckError()

    If Err.Number <> 0 Then
        WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description
        Err.Clear
    End If

End Sub


If Not WScript.Arguments.Named.Exists("Network") Then
    WScript.Echo "Network not defined"
    WScript.Quit(1)
End If


NLBConfiguration

cd C:\ConfignlbAdditionalVips
cscript ConfignlbAdditionalVips.vbs /Network:External