Charge them $5K for the solution so that they think you spent a lot of time looking for the answer to their problem. Depending on how many serial numbers appear on each line, create a large UDF so that they could store the information. Then create a Crystal report to search for the information. Then charge them 10K for the extra effort involved. Now THAT's value.
If you wanted to make the Excel Query even simpler, you could make the SN a parameter value, then make create a cell that this value is entered into. Then refresh the query. ONLY the detail lines that contain this value will be returned.