Bond Yield to Maturity using the Yield function in Excel

Hi all,
The yield function in excel does not give the right value if I play around with the redemption value(% of par). I have checked this with other available online bond yield calculators such as
http://www.moneychimp.com/calculator...e=calc_bondytm

If I change the redemption value to 50 and the bond price to $50, ideally the coupon rate and the yield should be equal for any time period. While this happens in the calculator mentioned above, Excel gives me a different number. Is this actually a bug or am I missing the point?

Test this in Excel...

=YIELD("6/30/2009","6/30/2022",0.0958,50,50,2,0)

Also test different redemption and price values and compare them with the calculator above.