By DD-MM-YYYY are you assuming numbers for each place? A mask like ##-##-####...? You can't really mask the date values specifically (to limit MM to 01-12 but not 13 for instance).
I don't have a lot of experience with MaskEdit but I think you can set the mask to ##-##-####.
Come to think of it, is this a .NET control? Do they still have a MaskEdit control? Or are you saying you want to limit a textbox to the DD-MM-YYYY format programmatically?
If you want your own custom format, you can put something in the Validating event. Check the Text property against your "mask" (or use a DateTime variable to see if it's a valid, recognized format). If it fails, set the event args Cancel to true and do whatever else you want (change the BackColor, etc.).
-Ner