Outlook automatic email reminder

I need Outlook to be able to generate an automatic email when there are less than 19 days left within the month.

I have a formula which i currently use in Excel

=IF(DATE(YEAR(TODAY()),MONTH(TODAY())+1,0)-(TODAY())>18,"","19 DAY RULE INFORCE ")

so for month this message should appear on the 12th june.. as there are 19 days left within the month.

On july it should be the 13th .. and so on

I have attached an email example

I want to be able to save the file within outlook with instructions on how to save the file...

It shouldnt take to long so the max iam willing to pay is £15 total