是这个意思？？
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;
type
TForm1 = class(TForm)
procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
OX,OY :Integer;
First :Boolean;
implementation
{$R *.DFM}
procedure TForm1.FormMouseMove(Sender: TObject; Shift: TShiftState; X,
Y: Integer);
begin
if not First then Canvas.Ellipse(ox,oy,ox+150,oy+150);
Canvas.Ellipse(X,Y,X+150,Y+150);
OX :=X;
OY :=Y;
First :=False;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
with Canvas do
Begin
Pen.mode :=pmNotXor;
Pen.color :=clBlack;
pen.Style :=psDot;
Brush.Style :=bsClear;
end;
First:=True;
end;
end.
][