perhaps something along these lines?
declare @param1 varchar(5)
set @param1 = '2701'
select *
from branch
where branchcode = (case when @param1 = '-' then branchcode else @param1 end)
set @param1 = '-'
select *
from branch
where branchcode = (case when @param1 = '-' then branchcode else @param1 end)
Duane.