Display external text in article

I want to integrate in my articles external texts from 3rd party services.

I have a link to a blank page with only some text that is changed daily…the link looks like:
http://www.acvaria.com/partener-acvaria.php?z=berbec

The bold text may be different, so I need to create a function in function.php that is called in an articles like [function=berbec] where function is the function name and berbec is the token. If I use another token, the link will have that token in it.

The function will read the text from that link and will display in a <div>. The reading must be done whenever the page loads, because the text may be changed meanwhile.

Need help!