preposition for instrumental?

Instrumental in my progress
instrumental to my progress

can both be correct?
I’ve seen in with instrumental when a gerund follows, so it’s not flat out wrong.

I vote for “in”.

Possibly “for” in some contexts, but “to” does not sound right to me.

Yes I wrote “in” first but I started doubting myself.

Who cares? Who is going to correct you? Who is going to mark you down for this? Where is it written which prepositions are correct and which are not?

These are serious questions. And here’s an even more important one. What is the complete sentence? In context, there may be subtle shades of meaning that are conveyed by “to” rather than “in”.

There are no right answers to usage questions. You look at each case individually. And if you can’t see any difference between “in” and “to” then it’s likely your reader won’t be able to either. If you can, then whichever one is right for your context is the right answer.

I would use different ones depending on the context.

Sarah was instrumental to my progress as a good person.
My learning to read music was instrumental in my progress in becoming a musician.

I believe the difference is whether or not it is something I did (in) or someone else (to). But I could be wrong.