"I still have some questions for Mr. Smith"

If I want to say: "I still have some questions for Mr. Bla-bla".
Do I say in german: Ich habe noch einige Fragen für Herr Bla-bla
or: Ich habe noch einige Fragen an Herr Bla-bla

Thanks for the assistance.

either but I'd go with an - but it's Herrn

I was also thinking about Herrn afterwards.
So it's ok either way. Thanks!

I would use "an" if I wanted to ask Mr. XX questions and tell sb. else about my intention. "Für" is uncommon in this case.
"Für" if I had written down the questions and wanted to give them to Mr. XX's assistant.