You could make 3 fields in your query, like this:
Val1: iif ([30 Day] > 0, 1, 0)
Val2: iif ([60 Day] > 0, 1, 0)
Val3: iif ([90 Day] > 0, 1, 0)
Then a fourth like this:
Sum: [Val1] + [Val2] + [Val3]
Sort it by [Sum] and set the Top Values propery to 1.
That should do it. I don't know if...