Delayed spell with a trigger?

[Greywander]

Is there any way to cast a spell on someone, but have the spell's effect be delayed until some sort of trigger? Sort of like a curse that activates when the target does something specific. About the closest I can think of is the Suggestion spell, specifically, where you make the trigger part of the suggestion (e.g. "When X, you should do Y"). Geas is another highly specific example where the target does or doesn't do the specified thing, they take damage. But is there a more generalized version of this that can be applied to any spell? Naturally, Dispel Magic would remove the "curse", and Detect Magic would be able to see that the target was under some kind of spell, so anyone on guard would still have a chance to foil such a curse.

Also obligatory mention of Glyph of Warding, as I'm sure someone will bring it up. It gets close to this concept, but cast on a location, not a creature.

Honestly, I could perhaps see building an entire class around this concept. Sure, in combat you usually want a spell to take effect immediately, but out of combat a delayed spell can be very useful.

[JNAProductions]

Is there any way to cast a spell on someone, but have the spell's effect be delayed until some sort of trigger? Sort of like a curse that activates when the target does something specific. About the closest I can think of is the Suggestion spell, specifically, where you make the trigger part of the suggestion (e.g. "When X, you should do Y"). Geas is another highly specific example where the target does or doesn't do the specified thing, they take damage. But is there a more generalized version of this that can be applied to any spell? Naturally, Dispel Magic would remove the "curse", and Detect Magic would be able to see that the target was under some kind of spell, so anyone on guard would still have a chance to foil such a curse.

Also obligatory mention of Glyph of Warding, as I'm sure someone will bring it up. It gets close to this concept, but cast on a location, not a creature.

Honestly, I could perhaps see building an entire class around this concept. Sure, in combat you usually want a spell to take effect immediately, but out of combat a delayed spell can be very useful.

Maybe not a whole class. But the old Mark Of Justice (https://www.d20srd.org/srd/spells/markOfJustice.htm) spell does that. Could convert that over.

[Mellack]

Contingency sound like what you want, but it is limited to self only.