search a string and display several lines

dim a as string
dim i as integer
open file for input as #1
do until eof(1)
i=i+1
input #1, a
if instr(1,a,"MyText") then
exit do
end if
loop
close #1
dim list as listbox
dim tmp as string
dim j as integer
open file for input as #1
do
j=j-1
input #1,tmp
if j=i-4 then
dim k as integer
list.additem tmp
for k=0 to 17
list.additem tmp
next
exit do
end if
loop
msgbox "DONE!"
close#1