private void RenderSumColumn(Gtk.TreeViewColumn column, Gtk.CellRenderer cell, Gtk.TreeModel model, Gtk.TreeIter iter)
{
decimal Sum = (decimal) model.GetValue (iter, (int)ServiceCol.sum);
decimal Paid ;
if(model.GetValue (iter, (int)ServiceCol.paid) != null)
Paid = (decimal) model.GetValue (iter, (int)ServiceCol.paid);
else
Paid = 0;
decimal Debt = Sum - Paid;
if (Debt <= 0 && Sum != 0)
{
(cell as Gtk.CellRendererText).Foreground = "darkgreen";
}
else
{
(cell as Gtk.CellRendererText).Foreground = "black";
}
(cell as Gtk.CellRendererText).Text = String.Format("{0:0.00}", Sum);
}