I have a Workbook with a Date Cell that I use to schedule date & times when Clients request specific schedules. I also have a Calendar Workbook that I enter a Time and Date which posts into the Calendar information. What would hope to produce is a lookup or match or? That when I post a date in the calendar and save, I then could enter any date in my other workbook and if the dates matched, I would have a popup or something.

My best explanation of what I'm asking is when you call in for a hotel reservation and tell them at date, they plug that date in for all their rooms for availability, a window pops up and tells them if rooms will be available or not. 

Again I have One workbook that I enter information into with a date they request, then I have a separate workbook with a calendar that I plug the requested date into. Just want a warning when I enter the clients date requested that I know if that date is available without searching through my workbooks.

Thank You