Create Software for ASL Gloss

I would like to create software that uses both text and symbols. There are symbols that are used when glossing american sign language that are not available. Also needed is the ability to put a line (opposite of the underline) over a sentence and then add text above that line. Some people I have spoken to recommend that I create a font. I need advise. It seems that a person could simply add the necessary symbols to English text and boom, there is your software. However, I am computer illiterate and it may be much more difficult. I am happy to provide more details when necessary. Thank you!