Contributed By: Paul Thomsen [MS]
You could script it.  Here's a script that adds users to a collection.  Adding machines, and reading from Excel would be relatively minor modifications.

if wscript.arguments.count<>1 then
 wscript.echo "One argument please - the collection"
 wscript.quit
else
 newname=wscript.arguments(0)
end if

    Dim lLocator
    Set lLocator = CreateObject("WbemScripting.SWbemLocator")
    Dim gService
    Set gService = lLocator.ConnectServer(, "root\sms\site_WMA")

        'figure out the current user, as a resource ID
        Dim username
 Dim oWshNetwork
 Set oWshNetwork=CreateObject("Wscript.Network")
 username = oWshNetwork.UserName
        Dim ResID
        Dim User, Users
        Set Users = gService.ExecQuery("Select * From SMS_R_User WHERE Name
LIKE ""%" + username + "%""")
        For Each User In Users
            If UCase(User.username) = UCase(username) Then ResID =
User.ResourceID
        Next
        'you may want to handle the contingency of a user that is new to the domain and
        'hasn't been added (yet) to the list of SMS users

        'now to do the real work...
        'start by spawning a blank instance of a collection rule
        Dim CollectionRule
        Set CollectionRule =
gService.Get("SMS_CollectionRuleDirect").SpawnInstance_()
        'and give that instance the values it needs - this is an important
point, of course
        CollectionRule.ResourceClassName = "SMS_R_User"
        CollectionRule.RuleName = "ResourceID=" & ResID
        CollectionRule.ResourceID = ResID

        Dim oCollectionSet
        Dim oCollection
        Set oCollectionSet = gService.ExecQuery("Select * From
SMS_Collection")
        'walk through the enumeration that was returned from the collection
query above and
        'select the one provided as a parameter
        For Each oCollection In oCollectionSet
            If oCollection.Name = newname Then
                oCollection.AddMembershipRule CollectionRule
                If Err.Number = 0 Then
                    Wscript.Echo "You were added to the " + oCollection.Name
+ " collection!"
                End If
            End If
        Next