I have a windows form with a textbox tbLength that displays a length of time for a scheduling program. The user can enter a start date/time from a time picker field, and can enter a length - the combo of these 2 calculates the end date/time. I need Length to be in a proper timespan format 1.00:00:00, etc. How can I validate the entered value is OK? Can I force the entered format to be 99.99:99:99?