# cmd > [HTML Version](cmd_aui_control.htm) Parameter _cmd_, a string of up to 199 characters, specifies the command, DLL, keystrokes, or object reference (according to _ctype_) associated with clicking on the control. The choices are: • [Windows Command Line](windowscommandline.htm.md) • [Keyboard Commands](keyboardcommands_aui.htm.md) • [Shell execute](shellexecute_aui.htm.md) • [Subroutine (SBX)](subroutine(sbx).htm.md) **See Also** • The discussion on how to use an [Accelerator](accelerator.htm.md) key • The commentary in [Modal Dialog Box Control](modaldialogboxcontrol.htm.md) about customizing the "X" button behavior.