Specifying number of options selectable in Multi Select List Box

Hi,

Just wondering if there is a method for specifying an exact number of options able to be selected in a multi select list box? For example: I have 2 list boxes on my form, lstAvailGenre and lstSelGenre. Between these list boxes I have two command buttons, cmdAddGenre and cmdRemGenre that add or remove items from/to lstSelGenre. If I have 20 options in the lstAvailGenre list box, I would like to limit users to a maximum of 3 selections. Not sure whether this would be better achieved by phyically limiting the number of items selectable in lstAvailGenre (maybe by dimming out other options until one or more of the selected options have been de-selected) or by limiting the number of items that can be added to lstSelGenre. Any suggestions?
n00bCoderAsked:
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rockiroadsConnect With a Mentor Commented:
Are you saying on your multi select list, u want the user to select max 3 items only?

try this - listbox is called List0


Private Sub List0_AfterUpdate()

    Dim i As Integer
    Dim iSel As Integer
    Dim iIdx As Integer
   
    'Store current index
    iIdx = List0.ListIndex
   
    'iSel holds number of selected items
    iSel = 0
    For i = 0 To List0.ListCount - 1
        If List0.Selected(i) = True Then iSel = iSel + 1
    Next i

    'If more than 3 then, unselect last selected item
    If iSel >= 4 Then
        MsgBox "Sorry but you cannot select more than 3 items"
        List0.Selected(iIdx) = False
    End If

End Sub
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n00bCoderAuthor Commented:
That will do nicely. Probably makes more sense to place the limit on the destination list box rather than the originating list box, but you have given me the headstart I needed to do that myself.
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Rick_RickardsCommented:
Although this has already been answered I'll offer the solution I was working on at the time.

You'll find it runs a little faster since it only looks at items selected instead of everything in the list.  It also avoids the need to consider whether the list starts counting at 0 or 1 (it starts at 1 if the list has column headers and 0 otherwise).  Hence For i = 0 to List0.ListCount -1 breaks down as soon as your list box uses column headers.  If you wanted to loop thru the entire list for some reason (not really needed here but if you wanted to and easy way to write code that works either way would be to write something like...

For i = abs(Me.List0.ColumnHeads) to Me.List0.ListCount = 1
   'Code goes here
Next i


Private Sub lstMyListBox_AfterUpdate()
    Dim varItem As Variant
    Dim lngCount As Long
    With Me.lstMyListBox
        If (.ItemsSelected.Count > 3) Then
            MsgBox "Only 3 items can be selected", vbCritical, " Update Canceled"
            For Each varItem In .ItemsSelected
                lngCount = lngCount + 1
                If lngCount > 3 Then .Selected(varItem) = False
            Next varItem
        End If
    End With
End Sub
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