Hi @Joseph_Wood,
welcome to Coda Community
If I correctly got your point, the formula could be something like this:
[YourTable].Filter([DateColumn]>= Today()-Days(7) && [DateColumn]<= Today()).[Step].Average()
However, if you could share your document - or a sample of it - (through “share” link on top-right) it would be easier to figure out a solution.
I hope it helps.
Cheers!