If, else, then code

Please suggest me a code for the following:

All the mails should be send once daily at the first time of opening the file only and not the second time the file is opened in a day.

mail1 & mail2:

If the remark in column ‘ad’ is ‘send mail’ then only the mail should be deliver otherwise not.

mail3:

If the remark in column ‘ac’ is “-” Then send mail.

mail4:

If the remark in column ‘ac’ is “Expired” Then send mail4 mail only once and then stop sending mail in future.

Thanking you in anticipation.

Mukesh