Try making the tank a member of a small infantry group, and set formation to Vee. The second infantry group can be ordered to doFollow the tank.
Alternatively, give the tank lots of waypoints, at which it will pause. And/or synchro these waypoints with infantry waypoints.
The way to script it is to use doMove and distance commands. There may be one on the Ed Depot. If not, download my mission
Regina Proeliorum [(currently in the beta testing forum), un-pbo it and look at the script called Shilka1.sqs. Essentially, this does exactly what you want, though you will have to tweak it a bit. Borrow anything you like, just include my name in your acknowledgements.