Add text substitution for all words ending with certain letters I’d like to have automatic spelling correction in MAC OSX 10.7 for all words ending with certain letter sequences. It would help me a lot in my typing if all words ending with "...ao” were substituted by “ão”, for example.

Is it possible, or do I really have to add every word in Text and Language —> Text menu?
What you're looking for is probably a text-replacement suite that supports regular expressions.  They can be cryptic at first but once you learn the syntax, they are extremely powerful.

There was a previous question on another site that netted a product called Find and Replace It which looks appropriate for your usage.