Hi again,
I just got Goal Seek to behave better. Tools Options Calculation
Checked "Iteration," left the maximum iterations at 100 and reduced the
maximum change down to 0.000000. Goal Seek results are now:

Person Service Sales Product Sales Total Sales Ratio
100 $20,000.00 $13,333.33 $33,333.33 40%
200 $30,000.00 $20,000.00 $50,000.00 40%
300 $40,000.00 $26,666.67 $66,666.67 40%
400 $50,000.00 $33,333.33 $83,333.33 40%

That's better. :)
Regards,
Ian.