function CreateUniqueFileName(sPath: string): string;
var
chTemp: Char;
begin
repeat
Randomize;
repeat
chTemp := Chr(Random(43) + 47);
if Length(Result) = 8 then
Result := Result + '.'
else if chTemp in ['0'..'9', 'A'..'Z'] then
Result := Result + chTemp;
until Length(Result) = 12;
until not FileExists(sPath + Result);
end;
// Kullanimi:
procedure TForm1.Button1Click(Sender: TObject);
begin
label1.caption := CreateUniqueFileName('C:\temp\');
end;