Encadrer les coordonnées

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
With Application
    .EnableEvents = False
    .ScreenUpdating = False
End With
Cells.Interior.Color = xlNone
On Error Resume Next
Range(Cells(1, Target.Column), Cells(Target.Row - 1, Target.Column)).Interior.Color = vbRed
Range(Cells(Target.Row, 1), Cells(Target.Row, Target.Column - 1)).Interior.Color = vbRed
With Application
    .EnableEvents = True
    .ScreenUpdating = True
End With
End Sub

Dim Cel As Range

Private Sub Worksheet_Activate()
Set Cel = ActiveCell
End Sub

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
 With Application
     .EnableEvents = False
     .ScreenUpdating = False
 End With
 On Error Resume Next
 Range(Cells(1, Cel.Column), Cells(Cel.Row - 1, Cel.Column)).Borders.Value = 0
 Range(Cells(Cel.Row, 1), Cells(Cel.Row, Cel.Column - 1)).Borders.Value = 0
 Range(Cells(1, Target.Column), Cells(Target.Row - 1, Target.Column)).BorderAround ColorIndex:=3, Weight:=xlThick
 Range(Cells(Target.Row, 1), Cells(Target.Row, Target.Column - 1)).BorderAround ColorIndex:=3, Weight:=xlThick
 With Application
     .EnableEvents = True
     .ScreenUpdating = True
 End With
Set Cel = ActiveCell
 End Sub