ok, so you mean you need first to learn how to do this :
so maybe it's better to try this first without vba:

in A1 put "01 - first choice"
in A2 put LEFT(A1,2)

here it is, and i thing you do not need more.

so, if in A1 there's a dropdown list of choices (see this post if you
need more data

)

if you are making the list of choice in vba, I suppose you know how to
do this and you can use the same in left function (also available in vba
code)