can some one plz send me an example on how to do a script that changes the route cost when there is no wan connection avalible on a certain interface so the other one will take over and be used until the primary is back online

if you want to use other link only when first one is down you can simply add another route with higher cost. and on the first one set up check-gateway=ping (or arp)

yes that would be the case but im running load balancing pcc with three wan connections and if the cost changes it keeps on working it only stops working when the route is disabled

Have a look at this post:

http://forum.mikrotik.com/viewtopic.php?f=2&t=53090