Trying to add new sheets for another part in same drawing, but properties are locked to original part file?

Hi,

I am creating a fabrication drawing & I am using 3 files. I have custom properties for each file that I want linked to each page of the drawing. However, all of my custom properties in my drawing are linked to my first part that I inserted into the drawing...each part displays the same mass in my drawing (the mass of part 1) !! It's very frustrating. 

How do I ensure that the custom properties for each page are linked to the part that is on the page????

FYI I have add new sheets by clicking "insert new" but I get the same problem. How should I overcome this problem when I add new pages/sheets for different parts?

Any input welcome, thanks!

SolidworksDrawings And Detailing