Drop down box to populate text field exactly as per value

Hello,

I am creating an expenses form for the company i work for. The problem i have is that the nominal code for particular departments. For example Accommodation is 010 & Banqueting is 020. However when these options are selected and only populates '10' or 20' into the text field.

Is there a way using javascript so it populates the exact value that has been selected. Rather than losing the 0 at the beginning.

Thanks.