Possible to Restrict access to servlets (only local referrs)?

[ByronM]

Is it possible to restrict access to specific servlets to local referrs only? For example i have a form that users submit that i do validation on but it seems people directly post to the servlet.

I don't have access to modify the servlet itself very easily, so is it possible to use web.xml or htaccess rules to keep apache from posting without it being a local referr?

thanks!