Macro to automatically send screenshot to an email address if cell criteria are met

Hello Everyone,

Thanks for having a look at this one. I have attached a sample workbook, your help is appreciated:

Here's the background: The attached workbook has a worksheet with 3 columns of data. The blue cells contain dynamic data which remain empty when criteria is not met, and display "BUY" or "SELL" if the criteria is met.

I need a macro which can detect when any one (or several) of the blue cells changes from being empty to containing either "BUY" or "SELL". I need the macro to email a screenshot in a simple email (ideally with the word "ALERT" in the subject line). The email address is a GMAIL address.

I need the macro to run every 20 seconds.

Could somebody please help me and get this to work?

Many thanks!