Border problem

[xsmurf]

Hello,

In my worksheet i have a range of data form column B to AG.
Within these columns i hide the colums where is no data in row 5.
And here comes my problem, when i want a xlmedium border around this new range it doesn't do what i want.
Al the edge's are xlmedium, except the edge on the far right (last column), this one is always xlthin.

How is this possible, when i selected the range within the code.

hope someone can help me.

Sub borders()

 Dim myBorders() As Variant, myBorders1() As Variant, myBorders2() As Variant, item As Variant
 myBorders = Array(xlEdgeLeft, xlEdgeTop, xlEdgeBottom, xlEdgeRight)
 myBorders1 = Array(xlInsideVertical, xlInsideHorizontal)
 myBorders2 = Array(xlDiagonalDown, xlDiagonalUp)

Application.ScreenUpdating = False

    sheets(Array("Jan", "Feb", "Mrt", "Apr", "Mei", "Jun", "Jul", "Aug", "Sep", "Okt", "Nov", _
        "Dec")).Select
    
    Union(Range(Cells(2, 2).End(xlToRight), Cells(19, 3)), Range(Cells(21, 3).End(xlToRight), Cells(38, 3))).Select
 
   For Each item In myBorders
    With Selection.Borders(item)
                  .LineStyle = xlContinuous
                  .ColorIndex = xlAutomatic
                  .Weight = xlMedium
    End With
Next item
    
   For Each item In myBorders1
    With Selection.Borders(item)
                  .LineStyle = xlContinuous
                  .ColorIndex = xlAutomatic
                  .Weight = xlThin
    End With
Next item
       
    For Each item In myBorders2
    With Selection.Borders(item)
                  .LineStyle = xlNone

    End With
Next item
Application.ScreenUpdating = True
End Sub