how can i tell if i have ented the same numbers twice in a column

I enter orders we receive for our business. I list them down in a column, is
there anyway I can tell if I have entered one more than once without having
to go back and check every time?

If you apply a conditional format to your column your can make duplicate entires stand out, so as soon as the second value is entered they will both change colour

If your data is in column A try the following in cell a2

=COUNTIF(A:A,a2)>1 entered under formula is in conditional formating and select a colour to highlight it

This can then be copied and pasted as formats to the other cells

If it does not work, check that excel has not enclosed the formula in quotes, if it has delete them!

Regards

Dav