[EpiData-list] EpiData Analysis interactive selection

I have a field UNITNUM with values for treatment units. I write in an EpiData Analysis program:

.... define u #### global set echo=on freq unitnum /vl set echo=off u=?Enter unit to analyze? select if unitnum=@u ....

to prompt interactively which of the many units I wish to select for subsequent analysis. Any suggestion, how to modify the program to be able to either make the selection for a specific unit (as now) or alternatively not to make a selection to analyze the full set?

Thanks for any suggestion,

Hans