!**************************************
    ! Name: TEdit Numerical Input Only
    ! Description:Limits the input of a TEdi
    !     t to numerical strings only by discardin
    !     g the "invalid" characters in its OnKeyP
    !     ress event handler
    ! By: Orlando Juriq
    !
    !This code is copyrighted and has    ! limited warranties.Please see http://w
    !     ww.Planet-Source-Code.com/vb/scripts/Sho
    !     wCode.asp?txtCodeId=1286&lngWId;=7    !for details.    !**************************************
    
    procedure TForm1.Edit1KeyPress(Sender: TObject; var Key: Char);
    begin
    if not (Key in [#8, '0'..'9', '-', DecimalSeparator]) then
    ShowMessage('Invalid key: ' + Key);
    Key := #0;
    end
    else if ((Key = DecimalSeparator) or (Key = '-')) and 
    (Pos(Key, (Sender as TEdit).Text) > 0) then begin
    ShowMessage('Invalid Key: twice ' + Key);
    Key := #0;
    end
    else if (Key = '-') and 
    ((Sender as TEdit).SelStart <> 0) then begin
    ShowMessage('Only allowed at beginning of number: ' + Key);
    Key := #0;
    end;
    end;