If you did mean dialog, try something like:
Code:
dialog Kewlio {
  title "KewlioMZX"
  size -1 -1 100 95
  option dbu
  box "",1,2 0 96 93
  button "&OK" 2, 21 40 60 20, ok
}

Also as Collective said
/help /dialog
in addition also try..
/help on dialog

On the other hand, you might of meant Custom Windows?
/help Custom Windows
Here is a tutorial on dialogs..
Dialog Tutorial