Excel time slot booking system

Hey Guys, I'm probably asking for a lot of help here but I keep running into a dead end.

Please find attached an example of the sheet.



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Essentially what I'm looking to do is organise how many people can be in a meeting at one time during a day so that we don't end up with too many people at the same time.

On the tab named "Entry" I'm hoping to have a form with a few entry tabs in F7 and below, these are self explanatory a few drop downs to select set options (team leader, advisor and code please see data tab).

With date entered in DD/MM/YYYY format, and time entered in 15 minute increments using HH:MM format. with "Reason" as simply Text. That is the simple bit!

What I'm wanting to do is have a macro which is ran after pressing the "Book Slot" button. Essentially what this will do is refer to the availability tab,

It will look up the date entered on the form, it will then check the Lines relevant for that LOB and Time on the Booked box on the Entry sheet. And it will then refer the number on that page against the information on the Availability sheet .

The idea is certain amount of people can book a single 15 minute slot so it becomes limited.
For this example, the date is the 05/01/2013 at 09:00-10:15 with LOB T1. It will be able to see that their is availability for this slot and allow it to be booked up.

Once booked the macro would add a 1 to the "Entry" tab in the relevant Slots (this example O11-O16), meaning only no one else could book that time up.

If someone then tried to book it, would be represented with a message stating "unavailable".

If the slot is available, it will then enter onto the database a line of the information originally entered for the basis of logging the interaction.

The idea is to manage the time effectively, i hope this makes sense?

so sum up.

-Enter data into form. Click book -> checks current booked VS Availability, either accepts or declines. If accepted adds information entered onto the form to the database section for logging.