Can I create a custom die roll as effect?

[nickabbey]

We're doing some homebrew of runestones and slots on weapons, and our artificer created a rune with a 30% chance of triggering the haste spell on the wielder whenever a hit lands. I know I can set an effect to pop on next action or roll, but I can't figure out either a direct or creative way to pop a d100 roll on a hit. Is this something I'd need to find or write an extension for, or is there maybe some kind of work around?

I figure a d100 table would work but I would like to have it pop automatically on hit if I could.

[LordEntrails]

Extension. At least with the 5E ruleset. Other rulesets might have other abilities, but since you didn't say, I can only assume.

[nickabbey]

Extension. At least with the 5E ruleset. Other rulesets might have other abilities, but since you didn't say, I can only assume.

You're right, 5e. That's why I posted it here in the 5e forum. Thanks for the feedback. I guess it's finally time to write my first extension.

[LordEntrails]

You're right, 5e. That's why I posted it here in the 5e forum. Thanks for the feedback. I guess it's finally time to write my first extension.

And you are right! I missed that the post was in the 5E forum. Mea culpa