Try this spreadsheet in Excel 2003. It uses the TINV function.
T Score from inverse confidence and degrees of freedom. Uses two tailed
probabilities.
95% 0.05
97% 0.03
99% 0.01
Sample size 10
degrees of freedom 9
tscore 95% 2.262
tscore 97% 2.574 <== This is an impossible value.
tscore 99% 3.250 It must be between 2.62 & 3.25

There appears to be a serious bug in the TINV function. The content of the
tscore column C cells is: =TINV(C5,$C$8)
Try it. This doesn't work correctly. MS needs to fix it pronto. Hard to
notify them.