Connect a custom panel to an exiting custom table

We are in the processing of upgrade our HR/Payroll from Abra Suite to Sage HRMS 2015. I tried to setup a custom panel for the no longer existing pralloc table because we need this table/data for our side systems. We convert the FoxPro table to SQL and copy it to the SageHRMS_Sample database. When I create a custom panel and bind data, I only can select a field from the main employee table or add a new field to the “Employee Custom File” database.  I cannot select “pralloc”. I just wonder if anyone know how to connect a custom panel to an existing table. Many thanks.