Retrieve, manipulate and update list

I have read with interest postings on this message board hopefully I am in the right place for some guidance.
I am trying to retrieve, say costs to date for a project from a data list, idealy within Excel and after further calculation I am looking to update the costs to date within the data list.
I have looked at LOOKUP and even Advanced Filter but the final updating of the original costs currently escapes me. I would welcome any help or pointers as to where I should be heading.
Thanking you in anticipation
S