i had a look at mirc help files for deltok and this is all i could see
$deltok(text,N-N2,C)
Deletes the Nth token from text.
$deltok(a.b.c.d,3,46) returns a.b.d
$deltok(a.b.c.d,2-3,46) returns a.d
You can specify a negative value for N.