Automatic Email Generation

Hi guys, not been here for a while as your help and support have moved me on leaps and bounds but this problem has stumped me totally.

I have an excel spreadsheet that I use to record when staff are due assessments on certain tasks. Currently I put their expiration date into the spreadsheet and that turns it green. One month prior to expiring it turns yellow and once expired it turns red. (conditional formatting)

What I want excel to do is be able to automatically send an email to the individual with a unique message relating to that competence (12 different competences available) letting them know it has expired and they aren't to carry out the task until they have been re-assessed.

Information:
Currently the email addresses are not in the spreadsheet but I can add them as a hyperlink to the individual users or simply add another column and hide it with their email addresses if that is whats required.

I don't actually want to have to open the document for this to happen, or to have to push a button.

I am using outlook as my mailer.

If you really need part of the spreadsheet I can upload but I don't feel it will add anything more than the information I've given.

Thanks for your time and look forward to your ingenious solutions.