Save as a text file - Naming Constrictions

Hi,

I've been working on a simple widget which records text messages which the user inputs, however the next function of this widget I have had some trouble with and that is saving it to a text file. I can save it the file perfectly fine, however I want to restrict the user to save in a particular style. For example "dayNumber_team_date_time.txt" where dayNumber must consists of 0-9 and team must equal "red, blue or white". Is this possible or are there some samples or examples available?

On a side note is it also possible to append the current date and time instead of the user defining it?

Thanks