Private Sub Rescale(x As Double, y As Double, _
                       xmax As Double, ymax As Double, _
                 ByRef xr As Double, ByRef yr As Double)
 
    If x < 1 Or y < 1 or xmax < 10 or ymax < 10 Then
       Throw New ArgumentException
    End If
 
    xr = x : yr = y
 
    If xr > xmax Then
       xr = xmax : yr = y * xmax / x
    End If
 
    If yr > ymax Then
       yr = ymax : xr = x * ymax / y
    End If
 
End Sub

Private Sub Rescale(x As Integer, y As Integer, _
                    xmax As Integer, ymax As Integer, _
              ByRef xr As Integer, ByRef yr As Integer)
 
    If x < 1 Or y < 1 Or ymax < 10 Or xmax < 10 Then
       Throw New ArgumentException
    End If
 
    xr = x : yr = y
 
    If xr > xmax Then
       xr = xmax : yr = CInt(Math.Floor(y * xmax / x))
    End If
 
    If yr > ymax Then
       yr = ymax : xr = CInt(Math.Floor(x * ymax / y))
    End If
 
End Sub