How to find an amount by adding other amounts (with file)

To include a file I had to restart a new post.

The problem is that cell B351 should equal R338. However B392 is short by the amount in R340 i.e. 29.06. B351 should be equal to R338.

So I was hoping to be able to do a piece of vba that would calculate the possibilities of having 29.06 by adding various amounts.

Thank you for your suggestions. I am not a programmer but I did some vba over 20 years ago, a bit rusted but I can still learn.