I was asked to give some advice on a spreadsheet for my father-in-
law. From an electronic measuring device it pulls in 4 sheets each
containing 400,000 rows of two columns; a time value and then a
measured value. Once the data is in the workbook a routine is run
that churns it all upp and spits out some results, a process that
takes about 20 minutes to run. A good chunk of the processing logic
is VBA code, which so far as I can tell runs single threaded.

This machine is a 3 Ghz quad core with 8 GB of DDR-2 memory and a fast
SATA HDD and the memory usage rarely goes above 600MB, CPU% is about
30 and the hard drive blinks only intermittently.

Is there any way I can make Excel better utilize the system resources
and run faster?