Louisa,
Access is an event driven database, so something has to happen as the database opens to cause a date check. There is an option to have a form open when the database opens, you could put the code there. Many people have a "Main Menu" that opens first so you can hide the code there, in the Form Open event, have it check, and pop the form it there are results. I have Access 2002 on this laptop, and the option can be set in Tools, Startup, in 2007 I think it is in Access Options, Current Database, form to open.
As far as the code is concerned your form can be bound to a simple query and the results displayed. Just change the form's default view property to continuous in case there are multiple records. The query would look something like this:
SELECT tblNewtork.CompanyName, tblNetwork.EndDate, DateDiff("d",EndDate,Date()) AS DaysOld FROM tblNetWork WHERE (DateDiff("d",EndDate,Date())>44));
The datediff function here uses "d" for days, there are many other options. The Date() is the date set on the computer being used. Be careful on the order, reversing date with enddate will get you a negative number which is somethings necessary but can produce confusing results. Hope that helps you.
Good Luck,
Privateer