ban list and watch list for constantly growing column of numbers

I have setup an excel sheet to record bar code numbers in column A from a barcode scanner. The data check formula checks for duplicates scanned that day (this is sort of a lobby check spreadsheet, recording the member number of entrants.) There is also a formula to time stamp any incoming information in column a and record the time stamp in column b next to the bar code entry.

What I would like to do is have two lists in column E and column F. One is a ban list....a list of numbers, that if any of the incoming member numbers in column A match any of the numbers in column E I will receive a pop up warning. The same for column F as a warning list.

I think conditional formatting would suffice over a popup....trying to figure out the formula now ...
I think I should be able to just expand the countIF function to include those two columns if do want to use a popup...just trying to figure out the syntax..

Any direction would be greatly appreciated. I know I am a newb.

Member Check.xlsx



Edit:

I am looking at INDEX MATCH and VLOOKUP...learning, but it is painstaking because I am at work...lol

bannedlist=Sheet1!$E$2:INDEX(Sheet1!$E:$E,COUNTA(Sheet1!$E:$E))
WarningList:=Sheet1!$F$2:INDEX(Sheet1!$F:$F,COUNT(Sheet1!$F:$F))

conditional format for banned: =MATCH($A1,bannedList,0)>0

I do this just for fun. Just click the "Add Rep" star at the lower left of my post.