Parametrization for dynamic Power Builder application

[qtptester17]

Hello,

I am trying to automate a powerbuilder application where individual fields are not recognized by the object spy.

 PbWindow("w_lems_login").PbDataWindow("dw_user_login").SelectCell "#1","usr_login", "username"
 PbWindow("w_lems_login").PbDataWindow("dw_user_login").SetCellData "#1","usr_pwd", "password"

1. How do I parametrize the script mentioned above?  Usually, I would use select datatable.value ("ID", "globalsheet"), but in this case I am confused as to how I would mention the cell number as well.
2. When I run the same script again, it runs sometimes, but at times I get an error.  Why is this happening?

Thank you in advance!!