Here is an example you can adapt to your specific situation :

Private Sub Worksheet_Change(ByVal Target As Range)
Application.ScreenUpdating = False
Dim i As Integer
Set Target = Range("b3")
If Target Is Nothing Then Exit Sub
'Clean whole sheet
Cells.Select
With Selection
.Borders(xlDiagonalDown).LineStyle = xlNone
.Borders(xlDiagonalUp).LineStyle = xlNone
.Borders(xlEdgeLeft).LineStyle = xlNone
.Borders(xlEdgeTop).LineStyle = xlNone
.Borders(xlEdgeBottom).LineStyle = xlNone
.Borders(xlEdgeRight).LineStyle = xlNone
.Borders(xlInsideVertical).LineStyle = xlNone
.Borders(xlInsideHorizontal).LineStyle = xlNone
End With
Range("B3").Select
'Adjusts to table
Select Case Target.Value
Case Is = "A"
i = 5
Case Is = "B"
i = 7
Case Is = "C"
i = 9
Case Is = "D"
i = 11
Case Is = "E"
i = 12
Case Is = "F"
i = 14
Case Is = "G"
i = 16
End Select

'Adjusts the table size
Range("D2:E" & i).Select

Selection.Borders(xlDiagonalDown).LineStyle = xlNone
Selection.Borders(xlDiagonalUp).LineStyle = xlNone
With Selection.Borders(xlEdgeLeft)
.LineStyle = xlContinuous
.Weight = xlMedium
.ColorIndex = xlAutomatic
End With
With Selection.Borders(xlEdgeTop)
.LineStyle = xlContinuous
.Weight = xlMedium
.ColorIndex = xlAutomatic
End With
With Selection.Borders(xlEdgeBottom)
.LineStyle = xlContinuous
.Weight = xlMedium
.ColorIndex = xlAutomatic
End With
With Selection.Borders(xlEdgeRight)
.LineStyle = xlContinuous
.Weight = xlMedium
.ColorIndex = xlAutomatic
End With
Selection.Borders(xlInsideVertical).LineStyle = xlNone
Selection.Borders(xlInsideHorizontal).LineStyle = xlNone
Range("B3").Select

Application.ScreenUpdating = True
End Sub


HTH