formula

[louise1111]

Hi looking for help on a formula 

I want to have cells A2  - A403 that have the EXACT 'numbers' in them. (duplicates)

Then the duplicates I want to take the information from their 'J column' 

and then concatenate the data into column L

I am getting stuck working out the formula please advise

Thank you 

Louise

[#2]

@louise1111 

In L2 it could be

=LET(colA, $A$2:$A$403, colJ, $J$2:$J$403, TEXTJOIN(", ",1,FILTER(colJ,A2=colA)))

and drag it down