Try using REPLACE_PATTERN but I'm not sure if it would with with the FIND action.
FIND Client WHERE (DISTANCE(REPLACE_PATTERN(Client.Address,',',' '), REPLACE_PATTERN(LoggedInSystemUser.CurrentLocation,',' '))<1000)
Or
Create a Not Persisted BO (Gmap) with the Gmap.ClientAddress and Gmap.CurrentLocation plain text attributes.
Then in your process you create the BO first and run the FIND action against this BO.
CREATE Gmap WITH Gmap.CurrentLocation=REPLACE_PATTERN(LoggedInSystemUser.CurrentLocation,',' '), Gmap.ClientLocation=REPLACE_PATTERN(Client.Address,',',' ')
FIND Client WHERE DISTANCE(Gmap.CurrentAddress, Gmap.ClientAddress)<1000