I have a table like the one below. How can I get Excel to put borders around groups with the same number in the 4th column so that there is a border around the groups. I was thinking conditional formatting could do it but I can't think how. So I think the only option is a macro. Could anybody help?

 1 64436 549419 1  
 2 64437 549420 1  
 3 64438 549421 1  
 4 64439 549422 1  
 5 64440 549423 1  
 6 64441 549424 1  
 7 64442 549425 1  
 8 64443 549426 1  
 9 64444 549427 1  
 10 64445 549428 1  
 11 64446 549429 1  
 12 64447 549430 1  
 13 64448 549431 2  
 14 64449 549432 2  
 15 64450 549433 2  
 16 64451 549434 2  
 17 64452 549435 2  
 18 64453 549436 2  
 19 64454 549437 2  
 20 64455 549438 2  
 21 64456 549439 2  
 22 64457 549440 4  
 23 64458 549441 4  
 24 64459 549442 5  
 25 64460 549443 5  
 26 64461 549444 5  
 27 64462 549445 5  
 28 64463 549446 5  
 29 64464 549447 5  
 30 64465 549448 6  
 31 64466 549449 6  
 32 64467 549450 6  
 33 64468 549451 6  
 34 64469 549452 6  
 35 64470 549453 6  
 36 64471 549454 6  
 37 64472 549455 9  
 38 64473 549456 9  
 39 64474 549457 9