Don't drink NyQuil recreationally. Find something that has dextromethorphan as the only active ingredient.
About the cough gels... it would take a lot of that to equal one bottle of Robo Cough. I'm not sure what the exact ratio is as I'm quite lazy with math. But the Delsym has 30mgs of DXM per 5ml? That's twice as much as robo. Very well, I'll keep that in mind.