Well then you do like they were saying. You use the read method to read and store all of the lines in the text document into a variable. Then you pull out the string you don't want, and then write the variable back into the file. So if you had a file with:
19273
2199
10382
And you wanted to remove 2199, you'd read all three lines and have them stored in your variable, so you'd end up with your variable being equal to "19273" NL "2199" NL "10382" then you just use something like strReplace on it to remove the line.