Random counting of cells to meet a given number

I'm looking for a formula which will pick a number of numbers and add then and try and get as close as possible to a given number. The number will not be met exactly but must not exceed the number, but I want excel to select the best possible numbers to ensure its as close as possible.

eg:
To get as close to 1000 as possible. (not over, must be under)

Range of numbers: 90, 300, 600, 500, 50.

We know that by picking 90+300+600 = 990 (10 remaining). Is better than 300+600+50 = 950 (50 remaining).

The data numbers I have is about 300 numbers not 5 numbers in the example above, is there a way when the formula selects the most appropriate numbers to total up, it will show which numbers have been selected?

Thanks everyone.

The problem you are trying to solve is one of typical programming tasks - bacpack/knapsack problem.
while description sounds simple, the actual computing power/time to find exact solution is enormous (already for mid-size datasets).
Reasonable description can be found on wiki: https://en.wikipedia.org/wiki/Knapsack_problem

The file posted by tim201110 has 3 algoritms of searching quite-good (but not necesserily best) solutions implemented
File (or parts of code) come from other (russian) forums - see the code itself for comments - they are written in cyrlic, so unreadable in plain english VBE,unless you change font into one with cyrlic alphabet - but ... can you read it? I do :-) ... but links to threads remained intact, like:
longdynamic: http://forum.sources.ru/index.php?showtopic=204375
slan: http://www.planetaexcel.ru/forum/ind...ID=8&TID=31231
etc.

To study these /and other algorithms with code commented in English, I'd suggest searching this forum (after short playing with our search engine i found some posts by shg, MrShorty, Alf and others...)