selecting texture for rotations

I have a 2d texture and a 3d texture and would like to rotate the 3d texture depending on the mouse movements. Is there any way that I can select the 3d texture before I operate on it.
thanks a lot,

Yes. Assuming the 3D texture lives on texture unit 1, simply:

glActiveTexture( GL_TEXTURE1 );
glEnable( GL_TEXTURE_3D );
glMatrixMode( GL_TEXTURE );
glRotatef( whatever );