Hide Rows While Using Date_Group

Content

I have an interval report that has a row for every hour of the day (column A).  I'd like to hide the rows where column B is null.  I'm able to do this until I use column B as a link to a drilldown level.  Anyone know a way around this?  Thanks.

UPDATE!  The issue really is hiding rows while using the date_group function.  I'm not able to use date_format because it removes logic for listing time in chronological order; in my case by hour of day.  The date_group function will list the hours in order, e.g. 11am, 12pm, 1pm, etc. but will not hide rows with no data, whereas the date_format function while hide rows with no data, but will not list the hours in chronological order, e.g. 1am, 1pm, 2am, 2pm, etc.