Dunnett C - where do I find actual p-values?

[Almut Hupbach]

Hello,
I hope someone can help with this.
I compared the different levels of a between-subjects factor that
came out significant in an ANOVA with Dunnett C (I chose this post-
hoc test because the error variances differ between the different
levels).  SPSS only gives the mean difference scores and displays an
asterisk for those that are significantly different from each other
at a .05 level.  Here is my question:  How can I calculate/look up
the actual p values for each comparison?
THANKS!
Almut