Okay not having this movies title is driving me nuts!!

In this movie a man goes to the city to run errands. His mother and young brunette fiancé do not want him to go. He goes with and envelope or briefcase I can’t remember is it is an envelope or briefcase. He shares a cab with a mysterious blonde women and they accidentally switch briefcase/envelopes. The blondes briefcase/envelope contains somthing mysterious (I can’t remember what exactly)
Well the man’s was somthing important he had to take care of that day so he try to find her and switch back.
This leads in on a wild goose chase through the city where unusual things keep happening.
Every new scenario he gets put in the blonde women is mysteriously involved. He is in a office and she is the secretary, he is in the doctors office and she is the nurse and he is at the mall and she is one of the models modling lingerie.
The rest is mostly kinda hazy. I could probably ramble up the memories for a few more facts if meet be.

I am pretty sure it was made in the 50’s
I watched it one late night on HBO about ten years ago. I THINK (but an NOT sure) one of the actors names was Micheal somthing he mat have been blonde and I had felt like I had seen him in other things.
It was in English.