比如第三行不要。
Dim lineNum as long,a$,b$
close #1
open "文件名.txt" for input as #1
line input #1,b$
linenum=1
do while not eof(1)
line input #1,a$
linenum=linenum+1
if linenum<>3 then b=b & chr(13) & chr(10) & a
loop
close #1
open "文件名.txt" for output as #1
print #1,b
close #1