How to set the offset for the components name in Eagle schematic?
I don't know how to modify Eagle itself to change its behavior as you describe, but this ULP script named renumber_by_page.ulp, written by Morten Leikvoll,  will rename all components in the format:

&lt;prefix&gt;&lt;page#&gt;&lt;localpageindex&gt;

Example:
5 R's on sheet1 will be renamed R100-R105
5 C's on sheet1 will be renamed C100-C105
5 R's on sheet2 will be renamed R200-R205


If you have more than 100 R's on one sheet, the 100th will be renamed R1100,
which could be mis-interpreted as an R on page 11, but normally you don't have
that many resistors on one sheet.

Special case, if your components have a name like ICxxxA (i.e. one section of a package), the suffix A will be added to the new name, so IC1A becomes IC101A.

I tried this on Eagle 7.3.0 and it seems to work fine.