Updating an Attribute based on a die roll from a macro?

As the title suggests, I'm trying to come up with a clever way to change the value of an attribute by rolling a d20 in a macro. Here's the use so it makes more sense. In D&D 5e, Divination Wizards get an amazing ability called "Portent". Portent lets the wizard roll 2 d20's at the start of the day (after a long rest) and store those rolls for later. My idea was to create an Ability (macro) that would roll 2 d20's, and update 2 custom attributes (which I've named Portent_1 and Portent_2). Then I'd write another macro that would list those, and allow for one to be "used" (and make the value 0). So far I haven't found a way to store a rolled value as an attribute yet though. Any thoughts or suggestions (or useful links)?

I don't believe that you can write data to an attribute that way. I htink Token-mod( [Script] TokenMod -- An interface to adjusting properties of a token from a macro or the chat area. ) could write the data to a token's status bar, which could be linked to a sheet attribute...  Aaron has been working on a Char-mod script that could probably do this, but it has yet to surface.

This is not possible with a macro directly. You can do this with the API, a Pro subscriber perk. I'm almost done with a script for this, but there are some out there already that can do this. 

What he said. =D

The token linked to the Divination Wizard's sheet doesn't not have to be the Divination Wizard's token. A generic token used for this operation only, can be linked to the sheet and set as Vince mentions.