export/import tool

Hi

I have installed the export/import tool into my 1.5.6.4 store and works perfect

Just got a quick question, I have a extension installed called custom field and it displays custom text after the price on the produt page and was seeing as I got a lot of products it would be easier to export the products and was looking to import them again after entering the custom field text in one go on the excel file but the export excel does not include the custom text field from the column from the database

Can anyone point me in the right direction on how to amend the code and what files or files to include the custom field from the database and import again

the custom field is within the oc_product_description table and is called custom_field

Thank you in advance

Kind regards

Ian