Hi Rkeslar,
I can only assue that you want to do this for reporting purposes and they are curently unscheduled tasks which you want others to know they exist, but don't want them to see fictitious dates.
You could create 2 new colums with, say Start1/Finish1 and copy/paste the Start/Finish dates into there. Then hide the original Start/finish columns as well as the relevant bars on the gantt chart. You may also like to rename the Start1/Finish1 columns to something more relevant. Finally, select each date you don't want to show and backspace will give you a NA result.
Remember, these dates will not show any changes to the schedule, so this exercise must be done each time you want to report.
Hope this is what you're after.
Good luck.