Draw a line in a button of a toolbar

Hi, sorry, but i'm not english...i'm italian. I have a problem Whith the follow code i draw a line in a butto of a toolbar Graphics g = toolBar1.CreateGraphics(); colore=colorDialog1.Color; Pen myPen = new Pen(colore); myPen.Width = 4; g.DrawLine(myPen, 204,17,219,17) (variable colore are declared as System.drawing.color) this code are OK but if i enter mouse pointer in the button area they are redraw and the line disappear. How i can avoid the line area redraw??? tank and...excuse for my english!!!!! AlfaOne