Well, you can write some programming to get Cc and Cr from spreadsheet. But tedius.
What's wrong with the old method. It gives you a good feel for the accuracy when you plot manually.

yeah correct.. but it is time consuming..  

visual curve fitting, a pencil and a straighedge are all you need - and about 3 minutes (well reading glasses too, perhaps?)

Did it this week - no problems!

f-d

¡papá gordo ain't no madre flaca!

Might I suggest you have the plot put in the form of loge-logp. This usually gives two straight lines and the intersection is putatively the preconsolidation pressure.  You should be able to determine the "intersection" point and determine the "straight-line" equations (i.e., Cc; Cr).  Don't have the time to try it myself at present.
  Casagrande did some consulting work for our company in Canada before I joined - my mentor was a student of his.  One of our engineers did a whole lot of e-logp constructions and kind of beamed with pride when showing Casagrande.  He looked at the curves and made a few adjustments - that didn't fit the "model" we all learned.  When asked, he intimated that he came up with the procedural construction so that he could "teach" his students.
  Question as to why are you still plotting e-log p anyway rather than strain-log p.  The latter gives Cc/(1+eo) directly.  and, you don't have to guess at the Gs value or do the test.