[Pharo-users] How to make an input field with some formating abilities

What I want is to create a morph that has the ability to input text from the user that formats it automatically and allows for a limited amount of characters. This input field will be in the format of HH:MM:SS , (H)our (M)inute (S)econd. The : seperators will be entered automagically by the input field and of course the input field should accept numbers and preferably sensible ones , so seconds and minutes will have a maximum of 60, hours 24. Is this possible with the existing Morphs or is this something I must implement myself ? I have been looking to the textmorph and all its subclasses but I have not made a lot of sense out of it, it looks very messy code.