Trying to add UDF for Last Updated (date for standard cost) for use in Price Updates

We are working on an eCommerce site that is linked to our MAS90. I have an import job created that I use for internal price updates that uses the CI_Item table. 

I am wanting to add an Update Date field to the Import Job, but can't find that anywhere. This was at the suggestion of the company who set up our link between the Website and Sage. These were his instructions:

To add an update date and update time column to the file being used to update pricing in MAS. Add those two fields to the Import Job. Then Magento will see that the records have changed since the last sync. 

That sounds super easy, except that I can't find anywhere that an update date field exists. I am attempting to add a UDF to the Item Maintenance Table, but wanted to be sure that was the best course of action. 

I'm also wondering why our Import Job to update pricing uses the CI_Item table vs the I/M Inventory Item Masterfile.

I don't need an update time field because we don't update pricing that often. 

Any insight you can provide would be greatly appreciated.