The way I see it you have two choices - either alias the fields to be the same, or rename after loading with a rename map.
If you choose the first, you use As aliases in the load:
LOAD ITEMID As ItemID,
ITEMNAME As ItemName,
To rename using a map, create an inline or file sourced mapping table with two columns, ProgressName and SQLName, like this:
Mapping LOAD * Inline
Load the Progress data first, and then after loading (before loading the SQL data):
Rename fields using FieldMap;
(You cannot rename a field into an existing name, so any renaming must be done before the other data is loaded.)
Hope that helps
sorry that my reply took this long. I have been out of office and didn't have possibilities to reply.
Renaming helped me to proceed and like J.D. mentioned the loading order was the main thing. I tried different loading orders and with that I got this working.
Thanks for pushing me to the right direction.