Assuming the combinations are of two amounts only from SheetA, there is a fairly simple way of doing this.
Create a new Sheet - SheetC. In Column A, paste the "Amount" column from SheetA, e.g. from A2:A50 (depending on how long the list is).
Use Paste Special - Transpose to paste the "Amount" Column again in SheetC, but transposing it so that the column turns into a row, e.g. from B1:AX1.
You will now have all your amounts in SheetC twice: once in Column A, and again in Row 1.
You can now easily use all the cells in the table to add every combination. I.e.enter in cell B2 the formula
=$A2+C$1, then copy this to every cell in the range, e.g. B2:AX50.
Once this is done you can go into SheetB where the combinations are, copy an amount to clipboard. Then go back into SheetC, and Find (Ctrl+F), inputting that amount from clipboard. Excel will find it for you somewhere in the table, and you can then see the amounts its made of and easily work out which amounts in SheetA these are.
You can then refine this method by using
MATCH() in SheetB to automate finding the value in SheetC which corresponds to each value in SheetB. Using the returned number you can get excel to get you the names of each of the constituent amounts with the