display multiple cell values in one cell on a different worksheet

would like help with this, not sure if it is possible or not. hard to explain so i will lay out exactly what i need to do. refer to spread sheet attached.
i have part numbers that may be on an open PO(Purchase Order) or multiple PO's. in sheet 7 column L i would like to show the open PO(s) #'s. if there are multiple PO's for one part number is it possible to list those PO #s(in 'OpenPO' column C) and drop down one row for each PO number? and then have the remaining of the worksheet info drop down with it? the reason i would like the part numbers with multiple PO #'s to drop down is i am adding in extra info for each PO #.
if this cant be done how can i have all the PO #'s listed in one cell in Sheet 7, column L?