Add & Delete Drop-downs

i have a soccer-site, on which of course,
can be kept track of played matches.
Now the admin has to be able to set the number
of goals, and then select who scored what goal.

I want a system where one can put a number in
a textfield (NaN would return an error).
Say the admin enters Ɖ'. Then three dropdown
lists appear below that field, in them are the
players.
If he turns Ɖ' (goals) into ƈ', the lowest one
has to be deleted, but the upper two have to stay,
with an unchanged (already selected) value ...

Preferrably cross browser. I just can't seem to
figure out, i've tried loads of innerHTML and
document.write(), both didn't give me what i
wanted (yet).