Finding The Match With VLOOKUP

I have some intersting issue. Actually there are lot of functions in excel but my purpose is somewhat is solved by VLOOKUP , MATCH, OFFSET, INDEX functions.

Prob: Here i have a database contains as below
A1 B1 C1 D1
111 123 i/p o/p
222 301
111 321
333 456

If i keep 222 / 333 in C1 i will get output at D1 as 301 / 456 respectively. But if i keep 111 , i want a desired result to be most lastly updated value in the array that is 321 but it is printing 123.

let say if have
A1 B1 C1 D1
111 123 i/p o/p
222 301
111 321
333 456
111 500

then if i enter 111 in C1 then i want to get 500 but still am getting 123 only. tht is the first hit.
i want to return a value which has lastly updated.

So if i use any fuctions from above i may getting correct results for 222,333 but i want result for 111.

Thoughts and rules:
1.The new entry will added at the end of the array.
2. A1/B1 are only numbers.
3. free to use any functions

U can have flexibility to create one more array or even update the column B1 if any i/p matches in column A1. So there will always a single output for each unique input.
Imean to say u can have a array with

A1 B1 C1 D1
111 321 (replace 123 with 321) i/p o/p
222 301
(remove this entry)
333 456