Question about dummy variables

[kurarinS]

Hello,everyone
As my topic is to investigate the difference of firms' financial performance before and after listing. So I need to put a dummy variable in my regression, namely ,if the firm is already listed ,d=1,otherwise d=0
however,my sample contains more than 1000 firms,and each firm have different listing date. so it is impossible just set a time-series dummy (namely year before 2005 ,d=0,year after 2005 d=1)
so ,how to put dummy variables based on individual firm.
thanks

[EViews Gareth]

You'll have to explain what you're doing in more detail.