How to execute functions simultaneously in this case?

Projects Programming
14 
tvoid toggle( bool state ) {
    switch( state ) {
        case true:
            digitalWrite( LIGH_PIN_14, HIGH );
            for( int a = 0; a < 3000; a++ ) {
                OneStep( false );                         // forward
                delay( 5 );
            }
            break;

        case false:
            digitalWrite( LIGH_PIN_14, LOW );
            for( int a = 0; a < 3000; a++ ) {
                OneStep( true );                        // backward
                delay( 5 );
            }
            break;
    }
}