The easiest way is to not actually use mirc to upload the file. I found a very simple method that uses the built in ftp.exe that windows has.

Code:
;mirc code
run -n ftp.exe -s:D:\Programs\mIRC7\ftp.do

;contents of ftp.do
open ftp.address.com
user
pass
cd public_html/webpages
put "D:\Programs\mIRC7\text.txt"
bye


The ftp.do file is a list of commands that ftp.exe will follow. The path of the ftp.do file and the file to upload have to be hard coded. Ask if you have any questions