I spent ages on this - tried to get it working using a route-map that matched routes advertised by R4 using the route-source in the route-map, but no joy whatsoever. Anyone else have any success using this method?
I know this doesn't fulfil the task correctly btw, but it should work no?
ip prefix-list r4 seq 5 permit 150.1.4.4/32
route-map 146 deny 10
match ip route-source prefix-list r4
!
route-map 146 permit 20
router ospf 1
distribute-list route-map 146 in