If you are using Outlook, it comes with a calendar and maybe that would be easier than building something in Excel.
Also there are small calendar apps available - like this one from Gregory Braun that lets you put reminders in any date - either as single reminders or as repeating reminders, including repeating say 1st Monday of each month.
If you still want to go down the Excel route, you can add a complete calendar to a spreadsheet. Excel has a built-in calendar.
I do not have Excel 2007 on this PC, so I can't test this now or walk you through it, but from memory, try this:
From the Ribbon select Developer (If it's not visible go to the Office Button, select Excel options at the bottom and select the Popular tab and check the 'Show Developer tab in the Ribbon' box)
In Developer - Controls select Insert and choose the Calendar Control - If it is not visible, click the additional controls icon - then find 'Calendar Control'. Select the control and draw it on the worksheet.
Resize the Calendar, then right-click and select Properties to change things such as font.
Right-click again and select 'View code' to add VB code to the control.
The calendar control allows you to use the date of the day selected by the user. Use the date to pop-up a message box with information based on the date selected.