Is comma needed?

[kohyoongliat]

I was walking with a briefcase, in which was the month's takings from the company.

Is the comma needed? Are there any errors in the sentence?

Thank you very much.

[Anglika]

I was walking with a briefcase, in which was the month's takings from the company.

Is the comma needed? Are there any errors in the sentence?

I was walking, carrying a briefcase

The comma would be better following "walking", so that briefcase and its contents are linked.

[kohyoongliat]

Thanks for the prompt reply.

You say, "The comma is better after 'walking' " but is the comma needed after briefcase?

If the sentence were to remain, is the comma needed after briefcase?