Opening brackets cannot be the first token in a line in mIRC Script.
while (%current <= $snick(#,0) )
{
turns into
while (%current <= $snick(#,0)) {
Btw why are you messaging people with "xdcc list" that doesn't sound too kosher to me.
mIRC is not designed for mass file sharing, you should use the proper tools for that like an ftp client, Kazaa or the likes.
Also might want to take a look at
this