HELP with STDEVPA and Returning Multiple Individual Values

Hey guys,

I'm having trouble with writing an equation that would help me perform a STDEVPA function on sales for each individual item sold in the past year. The Sales Record raw data sheet has thousands of records, with each individual item having multiple sales transactions. My goal is to reference the item number and bring back multiple individual values for each of the item number to derive their standard deviations. I've tried using the Index, Match, Small, Row functions but am not experienced enough with those to write an equation that would help me.

I'm really hoping you guys can help me with this. Sorry, I can't attach my workbook for security reasons.

Please find an over-simplified mock Sales Sheet attached that should help make it easier to understand.

Mock Sales Sheet - Excel Help.xlsx

Thanks in advance!!