Automating filling in a web form field with data from a text file

[BrettStah]

There's a website that lets me add input some text data into a form field, then I click a Submit button, then the page refreshes and lets me add more text data. (The submitted data goes into a database). The issue is I have a lot of entries to make, and there is apparently no built-in import option that would let me add in all text data in one operation.

So do any of the auto-fill extensions/add-ons for Firefox (or IE for that matter) support doing something like this? I basically can get the data that needs to be inputted into a text file with each piece of data on a separate line. I just need something that can parse that file line-by-line, put the contents of each line into the web form's text box, click Submit for me, wait for the page to refresh, and then move to the next line of the text file. I could "roll my own" utility, but I'd hate to re-invent the wheel if I don't have to...