You can create an update query to update that field for the criteria of those records with the selection of the list box and then call it:
Code:
Dim strRecordsToUpdate As String
Dim varX As Variant
strRecordsToUpdate = "In ("
For Each varX In Me.YourListBox.ItemsSelected
strRecordsToUpdate = strRecordsToUpdate & Me.YourListBox.ItemData(varX).Value & ", "
Next varX
strRecordsToUpdate = Left(strRecordsToUpdate, Len(strRecordsToUpdate) -2
strRecordsToUpdate = strRecordsToUpdate & ")"
strSQL = "UPDATE YourTableNameHere SET YourTableNameHere.Notified = -1 WHERE YourTableNameHere.YourPrimaryKeyFieldHere " & strRecordsToUpdate & ";"
CurrentDb.Execute strSQL, dbFailOnError
Me.YourListBoxName.Requery
that is "air code" meaning untested but it should be close enough to get you where you want.
Bob Larson
Access MVP