Excel 2007 : Count number of blank cells between two words

Hi.. how do I go about counting the number of cells between two words?

I have multiple words (e.g., DM, DG) arranged in a column and in chronological order (as below). How do I count the number of blank/empty only cells between two words (i.e., between the first DM and DG?

Also how do I count all cells (with or without text) between DM and DG? Thanks v much.

11-Nov-10
29-Oct-10 DM
30-Sep-10 RL
31-Aug-10
31-Jul-10 DG
30-Jun-10
31-May-10
30-Apr-10 DM
31-Mar-10