Public ReadOnly Property OldZoomFactor As Single

Dim instance As ZoomEventArgs
Dim value As Single
 
value = instance.OldZoomFactor

public float OldZoomFactor {get;}

fpSpread1.AllowUserZoom =true; 

private void fpSpread1_UserZooming(object sender, FarPoint.Win.Spread.ZoomEventArgs e)
{
   listBox1.Items.Add(e.NewZoomFactor);
   listBox1.Items.Add(e.OldZoomFactor);
}

FpSpread1.AllowUserZoom = True 

Private Sub FpSpread1_UserZooming(ByVal sender As Object, ByVal e As FarPoint.Win.Spread.ZoomEventArgs) Handles FpSpread1.UserZooming
   ListBox1.Items.Add(e.NewZoomFactor)
   ListBox1.Items.Add(e.OldZoomFactor)
End Sub