I don't know if you've solved it yet, but this might work:

SELECT To_ver.*, Clients.clientkey, pickup.cloc AS pickup, dropoff.cloc AS dropoff ;
FROM To_Ver ;
LEFT OUTER JOIN Trips ON To_Ver.tripkey = Trips.tripkey ;
LEFT OUTER JOIN Clients ON Trips.clientkey = Clients.clientkey ;
LEFT OUTER JOIN Locations Pickup ON Trips.ipickup = Pickup.lockey ;
LEFT OUTER JOIN Locations Dropoff ON Trips.idropoff = Dropoff.lockey ;
INTO CURSOR foo

Arne