First, the theory/idea is to mark a field in the Call Log table record for each record imported into the cash orders table. I assume that a day's import is a reasonably small record count (1 or 2 hundred records or less ). If so I would use a looping routine to mark the records imported.
Create new field in call log table named Posting status,type TEXT, auto enter value "Unposted"
In script to import records include the "Unposted" status, and update them as they are imported.
Somewhat like this:
Enter find mode 
Set Field [Posting status; "Unposted"]
Set Field [Cash Order; "Yes"] //however you id a new cash order to import
Perform find 
If ( Get( Foundcount ) = 0 )
Go to Layout [ Cash orders Layout ]
Import Records  // however you set up the import
Go to Layout [ original layout ]
Go to Record/Request/Page [ first ]
Set Field [ Posting status; "Posted" ]
Go to Record/Request/Page [ next, exit after last ]
Show all records
Go to Record/Request/Page [ last ]
Enter Browse Mode 
Hope that gives you the idea,