Which pattern to use?

Problem:

I have to fill up PDF forms. The same fields have to be filled up using different formats for the value. For example there can be a date field like @today_date@ or @today_date_in_words@. Similary @number@ or @number_in_words@.

Then there comes times frequently where requests come for more formats for the same fields.

My question is, can I handle this using some pattern so that I will not need to do lot of changes to the code, rather I can just plug the new format and it gives me the desired result.