Make code faster/better best practices

[welchs101]

Hi all: I have the following section of code and i am trying to make it faster. Currently when this procedure runs the screen "changes" durings its execution. Now i know i can "turn off screen updating" and this will increase speed but are there commands in the code which will prevent the screen from updating. I know activating or selecting things causes the screen to change. Also, any inputs to make this faster/better would be greatly appreciated.

Sub compare_lists(droparray() As String, addarray() As String, userrange1 As Range, userrange2 As Range)

Dim Rng As Range
Dim x As Long
Dim cellitem As Range
Dim junk1 As String
Dim y As Integer
Dim junk2 As Boolean

x = 1
'Compares Current list of students to "new" downloaded list of students
For Each cellitem In userrange1
            'This is the downloaded new list of students
         With userrange2
             Set Rng = .Find(What:=cellitem.Value, _
                                LookIn:=xlValues, _
                                LookAt:=xlWhole, _
                                SearchOrder:=xlByRows, _
                                SearchDirection:=xlNext, _
                                MatchCase:=False)
            If Not Rng Is Nothing Then
                Application.Goto Rng, True
                'junk1 = Rng.Offset(0, 0).Value
            Else
                droparray(x) = cellitem
                x = x + 1
            End If
        End With
Next cellitem


x = 1
'Compares New List of students to current list of students
For Each cellitem In userrange2
        'This is the downloaded new list of students
         With userrange1
             Set Rng = .Find(What:=cellitem.Value, _
                                LookIn:=xlValues, _
                                LookAt:=xlWhole, _
                                SearchOrder:=xlByRows, _
                                SearchDirection:=xlNext, _
                                MatchCase:=False)
            If Not Rng Is Nothing Then
                Application.Goto Rng, True
                'junk1 = Rng.Offset(0, 0).Value
            Else
                addarray(x) = cellitem
                x = x + 1
            End If
        End With
Next cellitem

End Sub