There is no "out of the box" way to do this without writing some additional code, here is an example that checks for joystick buttons in the pre-auton function that may do what you want.

/*---------------------------------------------------------------------------*/
/*                          Pre-Autonomous Functions                         */
/*                                                                           */
/*  You may want to perform some actions before the competition starts.      */
/*  Do them in the following function.  You must return from this function   */
/*  or the autonomous and usercontrol tasks will not be started.  This       */
/*  function is only called once after the cortex has been powered on and    */
/*  not every time that the robot is disabled.                               */
/*---------------------------------------------------------------------------*/

void pre_auton()
{
  // Set bStopTasksBetweenModes to false if you want to keep user created tasks
  // running between Autonomous and Driver controlled modes. You will need to
  // manage all user created tasks if set to false.
  bStopTasksBetweenModes = true;

  // Set bDisplayCompetitionStatusOnLcd to false if you don't want the LCD
  // used by the competition include file, for example, you might want
  // to display your team name on the LCD in this function.
  // bDisplayCompetitionStatusOnLcd = false;

  // test if we are not connected to the competition switch
  if( !(nVexRCReceiveState & vrCompetitionSwitch) ) {
    // so no competition switch
    while( !(nVexRCReceiveState & vrCompetitionSwitch) ) {
      // 7U starts autonomous
      if( vexRT[ Btn7U ] ) {
        while( vexRT[ Btn7U ] )
          wait1Msec(10);
        // Start the autonomous task
        startTask(autonomous);
        writeDebugStreamLine("start auton");
        // wait 15 seconds
        wait1Msec(15 * 1000);
        allMotorsOff();
        allTasksStop();
        // short wait before we do that again
        wait1Msec(5000);
      }
      else
      if( vexRT[ Btn7D ] ) {
        while( vexRT[ Btn7D ] )
          wait1Msec(10);
        // Start the usercontrol task
        startTask(usercontrol);
        writeDebugStreamLine("start user control");
        // wait 105 seconds
        wait1Msec(105 * 1000);
        allMotorsOff();
        allTasksStop();
        // short wait before we do that again
        wait1Msec(5000);
      }

    wait1Msec(20);  
    }
  }
}