Any help will be very appreciated:

Item Amount
Number
1234 500
1234 20
1234 350
1234 95
5678 400
5678 200
5678 10
9101 600
9101 50
9101 5
9112 85
9112 155
9113 450
9115 256


I made up the above list. Is there any way that I can custom sort a
list in this way whe
first to have the Item number with the largest amount and then the same
item number with their corresponding amount from high to low
then have the second largest amount by item number and then the same
item number with corresponding amount from high to low.

for example:

the item number with largest amount is 9101 with amount 600, 50 and 5
second item the largest amount is 1234 with 500, 350, 95 and 20
and so on,

so the list will be sorted in this way:

Item Amount
Number
9101 600
9101 50
9101 5
1234 500
1234 350
1234 95
1234 20
9113 450
5678 400
5678 200
5678 10
9115 256
9112 155
9112 85

Thanks