That means you have to create 250 pages(menu items) with "CalculatorFileName" field. I am saying you have to have one page with parameters that will load appropriate calculator based on these parameters. If you can follow the convention then load:
/mypage?item=1 load calc1.js, calc1.css
/mypage?item=2 load calc2.js, calc2.css
/mypage?item=3 load calc3.js, calc3.css
...
that essentially translate in to load calc{%QueryString["item"]|(identity)GlobalAdministrator%}.css
for all you 250 files.
If for some reason the files name are not following anyconvention i.e. you have mycalc.js supercalc.js, somecalc.js etc you can put all these in custom table with the fields itemid, jsfilename, cssfilename. Again using macro you can query you custom table get the filenames from there. Custom table gives you the ability to search, manage files. You can list items from custom table etc using repeater etc. In my opinion it is a much better approach then 250 pages. The bottom line is: one page, one template, one place to manage files.
If you want to create 250 pages - I would create a new page type for calculator pages. You can inherit from menuitem if you want to (in this case it will get all fields what menu item has).