Excel Add-In: P Value Calculator
Warning: When you download the add-in, make sure that you save it as an ".xla" file. Internet Explorer often changes the file extension to ".xls".
This add-in, PValue.xla, reports P values for normal, t (Student), chi-squared, F, and the Durbin-Watson d statistic. The user requests one or two tails (when appropriate) and the output can be a graph of the distribution with the P value shaded.
Read the installation instructions, then right-click to download the PValue.xla file when you are ready.