Thanks Jimmy for your quick response. Thank you so much.
I use another loginc.. I introduce two field. to get the previous row end date and current row start date.. then i compare that.
to Tet the pervious row enddate i used
../my:group1/my:group2[count(../my:group2/my:enddate)-1]/my:enddate
To get the current row start date
../my:group1/my:group2[count(../my:group2/my:startdate)]/my:startdate
Thanks
Deva