Simplest way to apply sun damage for vampires?

[AwkwardPsyche]

Say the only modification I wanted to add to the player as a vampire is to make them actually take damage over time while outside, under the same exact parameters that make the message show up about the player's "blood boiling". I'm trying to find a way to do that but to make the least amount of modification to existing spells and effects in the process, so far with no success. Is there a way to go about doing this by only modifying the existing sun damage spells or only the magic effects and spells, or would I have to make a separate script to incorporate into a magic effect?