Dear experts,

i am developing a report using crystal 2008. i have a parameter as dropdown list and i have put it as optional and in the selection formulas i have put the following:
(
if ( isNULL({?fav2@select code,name from [@z_cust]})


or not hasvalue({?fav2@select code,name from [@z_cust]})

or ({?fav2@select code,name from [@z_cust]}) = '')


then {_Z_CUST.code}='999'

else
({_Z_CUST.code}= {?fav2@select code,name from [@z_cust]}))


The problem is if i don't select anything from the dropdown list it is giving an error "Parameter has no value"

thanks