Extract Data From Rows Above With Formula

Good morning! I'm working with a file (dummy data attached) that lists the contents of credit memos for online orders (prefaced with "ECOM" or "CC" in col. A) fulfilled by different sites (values in col. B with col. A rows which aren't "ECOM" or "CC"). Some sites received multiple credit memos so are listed multiple times (site 42 in col. B), while others received no credit memos so only list a site header record w/ no orders beneath (site 309 in col. B). The fulfillment dollars and site number list in the same column, but I'm looking to separate them into 2 different columns. I need the rows with orders to note the most recently-listed store account in a new column (demo'd in col. G) while rows without orders should list "N/A" - I will then filter out the "N/A" values per cols. J-L and have a finished output. I am unsure how to set this up as a formula, though - I imagine it may require OFFSET but wasn't finding anything that worked. Any help would be so appreciated!!

try this,

O3
=IF(N(M3),"N/A",LOOKUP(2,1/ISNUMBER($M$3:M3),$N$3:N3))

copied down.

Thank you so much, windknife - this worked perfectly! This is for a big project at work that is going to make life easier for 500+ different fulfillment locations, so I really appreciate your help!!