void __fastcall TForm1::Edit1KeyPress(TObject *Sender, char &Key)
{
  (dynamic_cast<TEdit*>(Sender))->ReadOnly = false;
 
   Set<char,'0', '9'> nst;
   nst<<'0'<<'1'<<'2'<<'3'<<'4'<<'5'<<'6'<<'7'<<'8'<<'9';

   if ((nst.Contains(Key)) || (Key == VK_BACK) ||
    ((Key == DecimalSeparator) && (Edit1->Text.Pos(DecimalSeparator) ==  0 ))
    || ((Key == '-') && (Edit1->SelStart ==  0 ) && (Edit1->Text.Pos('-') ==  0 )))
   {
    (dynamic_cast<TEdit*>(Sender))->ReadOnly = false;
   }
   else (dynamic_cast<TEdit*>(Sender))->ReadOnly = true;
 
}