Changing vector by matrix problem

Hi all, I am new to this and have a problem that I thought would be simple, but it appears not to be. I want to test collisions between objects. I have the Min and Max vectors of the mesh. However these values were those obtained from the model at the origin. My object has the following attributes: A D3DXVECTOR3 for its position, A D3DXVECTOR3 for its rotation, A Matrix that is the result of position and rotation What I would like to know is how do I update the Min and Max vectors so that they stay current with the model. I realise that when I increase the x,y or z values of the mesh I could also increase these points, but this sounds like it would slow things down to me. I would much rather just get the info from a matrix. Any help as always is greatly appreciated. Cheers Drb2k2