Mass Update, Pricing, Entered Cost, Multiple Vendors

I am experimenting with Price Updates using the in-built 'Update Prices' function.

The option to base the new sales prices on the 'Entered Cost' could be very useful, but it appears this uses the Purchase Price field on the Item, not the Purchase Price(s) shown on the Vendor sublist.

It also seems that I am unable to update the Purchase Price using the standard Mass Update functionality as this field is not available in the 'Mass Update Fields' screen.

I have found one of the 'special' Mass Updates that allows you to update the Purchase Price field from the last price paid, but this is of little use (as most changes arise from a supplier price increase, so we are trying to update our records before we create any Purchase Orders with the new prices on).