You could do this with VBA in the Worksheet, Selection Change event.
VBA Code:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Dim lngTargetRow As Long
If Intersect(Target, Range("M33:M1233")) Is Nothing Then
Application.EnableEvents = False
lngTargetRow = Target.Row
If lngTargetRow < 33 Then
lngTargetRow = 33
ElseIf lngTargetRow > 1233 Then
lngTargetRow = 1233
End If
Range("M" & lngTargetRow).Select
Application.EnableEvents = True
End If
End Sub
If the user hits the TAB key, it will likely stay in the same cell, but arrows, ENTER, or mouse should all work. There is likely a way to handle the TAB key, but I cannot think of it at the moment.
Hope that helps,
Doug