The CDF Collaboration has made a preliminary measurement of B(d)
mixing as a first step toward measuring mixing in the B_s system.  Flavor
tagging using opposite-side tagging schemes have been applied.  Results
agree well with precise results from the B-factories.  We use these results
to estimate CDF's B_s mixing range using the present data set (~ 250 pb-1)
and extrapolate to the potential from larger data sets in future running.