Lookup from range to display a row
 

Hi.. I have a table in the following format.

TABLE I
Name Total Amount due 30days 40days 50days
Alan 5,646.87 5000 646.87
Smith 653.22 653.22
Vijay 2000 1000 500 500

TABLE II
NAME AMOUNT DUE AGE
Alan 5646.87

Now is there a formula which I can put under Age column of table II to give
me how old is the amount due for. Eg. The formula should through up that the
amount is due for 30 days. Now I understand 5646.87 is not equal to 5000. But
I want the formula to calculate the next lowest number to 5646.87 i.e., 5000,
so my answer for above would be 30 days and not 40 days. Hence the formula
must display the value in row 1 of table 1 i.e., number of days.
Please also explain how the formula works.

Thanks