How is it more convenient to implement the check for the presence of an input value in Excel?

Question

excel

The person has a spreadsheet in Excel. A person enters the numbers of invoices for payment from different organizations there. Naturally, each organization has these numbers - who is in what much, but that's not the point.
It is necessary to make it so that a person can understand as conveniently and quickly as possible that he is entering an account number that has already been entered somewhere (within the corresponding column, of course) above in the table.
The idea of ​​searching by Ctrl+F with every input was swept away right there, because in this way a person will simply go crazy.
In Excel, there is auto-substitution of text, when you wrote, for example, a cell above "word", write "slo ..." below and Excel substitutes "... in". This is how it would be ideal, probably, when you dial the account number, and Excel immediately substitutes it if it has already been entered, but this does not work when the values ​​do not start with a letter, but with a number, and it seems like it does not work when two or more values ​​with the same "prefix".
I know Excel at the level of an ordinary user, with all sorts of macros and have never worked, even with formulas - a few times. But it's interesting to hear any suggestions.