Put this in your query analyzer. That is essentially what you are doing.
declare @var varchar(20)
set @var= '''dop'',''123'',''tlm'''
if 'dop' in (@var)
print @var +' won''t work'
If it is always two variables in that parameter, I would parse them out with text functions, assign them to variables, and change you select clause to incorporate the variables. If there are a dynamic amount of substrings in the parameter, you will need to come up with something else.