Thanks, 8老師. Last question

Assume I can get TN for company B's client. Is the following case legal?

When I go to meet with company A in US, I use my I-94 with H1B stamp on it. A few days later, if I need to work for B's client in US, I use another I-94 with TN stamp on it. Or, I can only have one I-94 at a time. That would mean each time when I cross the border by land, I have to get a new I-94 according to which company I am going?

Thank you very much.