vezerid gave me the following solution to my initial post (copied below),
which works wonderfully, but I forgot to mention 1 other criteria: I need the
formula to put a result in Column S based on the date in Column U (if there
is one), and stop calculating elapsed days as of that date.

vezerid's solution:
=IF(OR(AND(P15=1,TODAY()-R1530,U15-R1530),AND(P15=2,TODAY()-R1545,U15-R1545)), TODAY()-R15,"")

I am trying to write a conditional formula that calculates the number of days
outstanding, as described below. Here are the pertinent column designations:

Column P = Priority level (1 or 2)
Column R = Date Assigned
Column U = Date Closed
Column V = Status (Open or Closed)
Column S = Days Outstanding

If Column P is 1, and today is more than 30 days past Column R, and Column U
is more than 30 days past Column R, calculate Column S, BUT

If Column P is 2, and today is more than 45 days past Column R, and Column U
is more than 45 days past Column R, calculate Column S

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VB