Rotate around vector

RotOffset(vector offset, vector ammount)
{
    rotation vRotArc       = llEuler2Rot( ammount * DEG_TO_RAD );
    //-- creates a rotation constant, 30 degrees around the X axis

    vector   vPosOffset     = offset;
    //-- creates an offset one meter in the positive Y direction

    vector   vPosRotOffset  = vPosOffset * vRotArc;
    //-- rotates the offset to get the motion caused by the rotation

    vector   vPosOffsetDiff = vPosOffset - vPosRotOffset;
    //-- gets the local difference between the current offset and the rotated one

    vector   vPosRotDiff    = vPosOffsetDiff * llGetLocalRot();
    //-- rotates the difference in the offsets to be relative to the global rotation.

    vector   vPosNew        = llGetLocalPos() + vPosRotDiff;
    //-- finds the prims new position by adding the rotated offset difference

    rotation vRotNew        = vRotArc * llGetLocalRot();
    //-- finds rot to continue facing offset point
    //llSetPos(vPosNew);
    //llSetLocalRot(vRotNew);
    llSetLinkPrimitiveParamsFast( LINK_THIS, [PRIM_POSITION, vPosNew, PRIM_ROTATION, vRotNew] );

}

integer IS_ON = FALSE;
set_Rot()
{
    if (IS_ON)
    {
        RotOffset(<0,0,-(0.315/2)>,<0,-90,0>);
    }
    else
    {
        RotOffset(<0,0,-(0.315/2)>,<0,90,0>);
    }
}

default
{
    state_entry()
    {
        //llSay(0, "Hello, Avatar!");
    }

    touch_start(integer total_number)
    {
        IS_ON = !IS_ON;


        set_Rot();
        //llSay(0, "Touched.");
    }
}