Примерно так
program NewProject;
var
okCommand: command;
z:integer;
begin
// создаем форму
Okcommand := createcommand('Ok',cm_ok,1);
ShowForm;
addCommand(Okcommand);
while (getClickedCommand <> OkCommand) do
delay(100);
repeat
z:= z+1;
showCanvas;
setColor(0, 255, 0);
drawtext('Выполнено: '+ z +'%',0, 0);
repaint;
delay (1000);
setcolor (255,255,255);
fillRect(0, 0, getWidth, getHeight);
repaint;
until (getKeyClicked <> KE_NONE);
end.