I am sorry to ask a really stupid question but I just cannot get my head around how to hide an #N/A error when a cell in the argument has not yet been filled.

My simple formula is:

=VLOOKUP(A30, E5:F18, 2, FALSE)

I have been reading lots about 'IFs' and 'ISERRs' but can't get either of them to work. Clearly I am doing something wrong but my formula is definitely correct, it is just waiting for someone to type a code into 'A30' but while 'A30' is blank, I would like this cell to be blank too rather than showing an error.

Any advice would be greatly appreciated.