Hello @Clair_Arthur!
What you are looking for could be accomplished in a couple of ways but I believe the simplest would be a formula field!
If you table looks something like this:
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You could create a new formula field that uses an If statements to return a date based on the deadline and the asset needed:

Then you’ll get the date 7 days before the deadline populated automatically:

You could also chain IF statements to handle different needed assets:
IF(
{Assets Needed} = "Get gift note",
DATEADD(Deadline, -6, 'days'),
IF({Assets Needed} = "Send extra merch",
DATEADD(Deadline, -3, 'days')
)
)
Let me know if I can help provide any more information, and if this helped answer your question please mark it as the solution :white_check_mark: .