procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
var
s:set of char;
i:integer;
begin
s:=['.',#8,'0'..'9'];
i:=pos('.',edit1.text);
if i>0 then
s:=s-['.'];
if (i>0)and(i=length(edit1.text)-2) then //可任意控制-2,-3....
begin
key:=#0;
exit;
end;
if not (Key in s)then
Key := #0;
end;