count distinct for a particular column

[emmas]

I need to loop through all rows of the grid (including not modified ) and count distinct data from a particular column. Is there a way to do that?
For example first row shows check# 11, second row check# 22, and the third row check# 11 again, the count distinct should return 2.

thanks

[sven]

This is an own algorithm. Simple get all models from the store, loop over them and count it as needed. You know the dataindex of that column, so you can check for douple entries.