$ManagementServer = ServerNameHere!
$SourceGroupID = GetComputerGroupIDFromDisplayName(DisplayName of SourceGroup)
$DestinationGroupID = GetComputerGroupIDFromDisplayName(WebAppName watcher computers group)

if (CompareComputerGroupMembership($SourceGroupID, $DestinationGroupID) -eq 0)
{
    SyncComputerGroupMembership($SourceGroupID, $DestinationGroupID, $ManagementServer)
}

function SyncComputerGroupMembership([string] $SourceGroupID, [string] $DestinationGroupID, [string] $ManagmentServer)
{
    ## load SDK assemblies
    [System.Reflection.Assembly]LoadWithPartialName(Microsoft.EnterpriseManagement)
    [System.Reflection.Assembly]LoadWithPartialName(Microsoft.EnterpriseManagement.Configuration)
    [System.Reflection.Assembly]LoadWithPartialName(Microsoft.EnterpriseManagement.ConnectorFramework)
    [System.Reflection.Assembly]LoadWithPartialName(Microsoft.EnterpriseManagement.Monitoring)
    
    ## connect to management group
    $ManagementGroup = New-Object Microsoft.EnterpriseManagement.ManagementGroup($ManagementServer)

    ## build include list xml items from source group childs
    $IncludeListXML = 
    $SourceGroupChilds = Get-ChildItem (Get-MonitoringClass  where {$_.Name -eq $SourceGroupID})  Sort DisplayName
    foreach ($SourceGroupChild in $SourceGroupChilds) { $IncludeListXML = $IncludeListXML + ( + $SourceGroupChild.Id.ToString() + )}

    ## get destination group's discovery configuration
    $DestinationGroup = $ManagementGroup.GetMonitoringClasses($DestinationGroupID)[0]
    $Discovery = $DestinationGroup.GetMonitoringDiscoveries()[0]
    $DiscoveryConfiguration = $DestinationGroup.GetMonitoringDiscoveries()[0].DataSource.Configuration

    ## create new discovery configuration
    $NewConfiguration = 
    if ($DiscoveryConfiguration.IndexOf() -lt 0)
    {
        ## include list present
        $Start = $DiscoveryConfiguration.IndexOf() + 17
        $NewConfiguration = '$MPElement[Name=Windows!Microsoft.Windows.Computer]$$MPElement[Name=SC!Microsoft.SystemCenter.ComputerGroupContainsComputer]$'
        $NewConfiguration = $NewConfiguration + $IncludeListXML + 
        $NewConfiguration = $DiscoveryConfiguration.Substring(0, $Start) + $NewConfiguration + $DiscoveryConfiguration.Substring($Start)
    }
    else
    {
        ## include list not present
        $Start = $DiscoveryConfiguration.IndexOf() + 13
        $End = $DiscoveryConfiguration.IndexOf()
        $NewConfiguration = $DiscoveryConfiguration.Substring(0, $Start) + $IncludeListXML + $DiscoveryConfiguration.Substring($End)
    } 
    

    ## set new discovery configuration
    $Discovery.Status = [Microsoft.EnterpriseManagement.Configuration.ManagementPackElementStatus]PendingUpdate
    $Discovery.DataSource.Configuration = $NewConfiguration
    $Discovery.GetManagementPack().AcceptChanges()
    
}

function GetComputerGroupIDFromDisplayName([string] $GroupDisplayName)
{
    ## returns the ID (name property) of the computer group specified by display name
    return (Get-MonitoringClass  where {$_.DisplayName -eq $GroupDisplayName}).Name
}

function CompareComputerGroupMembership([string] $GroupID1, [string] $GroupID2)
{
    ## use this function to compare the membership of 2 computer groups
    ## 2 parameters, IDs of the groups to compare
    ## returns 1 if the membership of the groups is identical, otherwise 0
    
    $GroupID1Members = Get-ChildItem (Get-MonitoringClass  where {$_.Name -eq $GroupID1})  Sort Id
    $GroupID2Members = Get-ChildItem (Get-MonitoringClass  where {$_.Name -eq $GroupID2})  Sort Id
    
    $GroupID1MembersString = 
    foreach ($Member1 in $GroupID1Members) { $GroupID1MembersString = $GroupID1MembersString +   + $Member1.Id.ToString() }

    $GroupID2MembersString = 
    foreach ($Member2 in $GroupID2Members) { $GroupID2MembersString = $GroupID2MembersString +   + $Member2.Id.ToString() }

    if ($GroupID1MembersString -eq $GroupID2MembersString) { return 1 }    else { return 0 }
    
}