(Untested idea).
Set up a UDT with numbers as the key value (01,02,03,04,05...29).
Set your report with an exclusive outer join (assuming this is possible in CR?), with a filter on UDT results equal to the number of spaces you want (parameter?).
Sort the UDT results first (somehow).
Suppress your sub-report (and any text fields, lines...) when the UDT value is not NULL.
...
------------------------------
Kevin Moyes
Technical Systems Analyst
Munjal White Consulting Co.
Toronto ON
------------------------------