depend where the adjustment is needed :
if the pins are failing the door will move up and down when you pick it up, also this can be caused by damaged hinges futher investigation would be needed on that though,
the door jam may need pumping with a porta power to keep door frame true,
but if it is only the striker on the b pillar you cant slighty let the pressure off it with an allen key and the tap it with a hammer if the direction required,
but as i read your post again my calais did the same and it was bad it was hitting the frame on the car this was due the hinge weld cracking in the A piller frame so i had the door held in the postion needed and then welded the hinge back in postion problem solvered
if it doesn't have a lion in the badge it not worth having