Here is my code:

If optName.Value = True Then
Dim strWhere As String
Dim ctl As Control
Dim varItem As Variant

'make sure a selection has been made
If Me.List1.ItemsSelected.Count = 0 Then
MsgBox "Must select at least 1 employee"
Exit Sub
End If

'add selected values to string
Set ctl = Me.List1
For Each varItem In ctl.ItemsSelected
strWhere = strWhere & ctl.ItemData(varItem) & ","
Next varItem

'trim trailing comma
strWhere = Left(strWhere, Len(strWhere) - 1)

'open the report, restricted to the selected items
DoCmd.OpenReport "rptEmployees", acPreview, , "EmpID IN(" & strWhere & ")"

I get an error :
complie error: method or data not found
at .ItemsSelected.