Need help with Vector Math

I have the following code that im trying to make work. i have a 2x2 meter prim, its a miniture representation of a sim. the code im trying to make will move a marker from 0,0, <NOT USING Z> to a point i spesifie, here is the tricky part, i want to convert Real world values <EG use a landmark and get the X+Y from it> so for example if i told it the x and y were x128 y128 then my marker would be in the center of my miniture sim map but my code just wont work, any help will be apreciated.

demo() 
{

    vector AvatarPosition=<128,128,321>; //This is my Real World Cordanates
    
    vector MapPosition=llGetPos(); // Get the current position of the marker
    
    vector MarkerPosition=llVecNorm(<AvatarPosition.x,AvatarPosition.y,0>);

    MapPosition.x=MapPosition.x-1; //Subtrackt 1M from both x and y so we end up at
    MapPosition.y=MapPosition.y-1; //Miniture map's <0,0,0>
    
    MarkerPosition = MarkerPosition * 2; //Times marker position so that we tell it that its 2 meter by 2 meters
    
    MarkerPosition = MarkerPosition + MapPosition;
    
    //That should have automatically corrected the Z, too.
    
    llSetPos(MarkerPosition);    
    
    
    
    
}
default
{
    state_entry()
    {
        demo();
    }

}

This code just likes to put it at a random position please help!!

This should do the trick. Untested, so can't be 100% sure.

This accepts the avatar position as the input, and returns a position in region coordinates. Set the marker position to that exactly.

This allows for a variable size base. Declare a global variable at the top with the size you want. It's a float, and it assumes x and y are the same. In your case, this will be 2.0

vector calc_pos(vector AvatarPosition)
{
vector MapPosition=llGetPos(); // Get the current position of the marker
rotation MapRotation = llGetRot();

vector MarkerPosition=<AvatarPosition.x,AvatarPosition.y,0>;
MarkerPosition = MarkerPosition - <128.0, 128.0, 0>;
MarkerPosition = MarkerPosition / 128;
return MapPosition + ((MapScale/2)*MarkerPosition)*MapRotation); //MapScale should be a global variable. A float value
}