I am currently grouping sprites together, then applying a rotation transformation on draw:

private void UpdateMatrix(ref Vector2 origin, float radians)
{
     Vector3 matrixorigin = new Vector3(origin, 0);
     _rotationMatrix = Matrix.CreateTranslation(-matrixorigin) * Matrix.CreateRotationZ(radians) *  Matrix.CreateTranslation(matrixorigin);
}

Where the origin is the Centermost point of my group of sprites. I apply this transformation to each sprite in the group.

My problem is that when I adjust the point of origin, my entire sprite group will re-position itself on screen.

How could I differentiate the point of rotation used in the transformation, from the position of the sprite group? Is there a better way of creating this transformation matrix?