Resolution:
To do FTP Manually from BW via external command will be using Windows ftp.exe to do FTP for example to Mainframe.

The, Batch file that BW will call via external command is like below:

=====------============------============------=======
@echo off

C:/WINDOWS/system32/ftp.exe -s:C:/ftp_command.txt &ltyourhost>
=====------============------============------============------=======

What BW will do is prepare an input file for FTP Program and then using 'Command line' Task it will invoke the FTP batch file like above that in turn will upload the file to FTP/Mainframe server.

Input File looks like :

=====------============------============------============------=======
&ltusername>
&ltpassword>
rebx220
put &ltinput_local_filename> &ltRemote_file_location_name>
Quit
=====------============------============------============------=======

First line is User Name, Second is Password and third one is actual command to execute - for now it's PUT and forth command is termination command.  

Pleas make sure all the value in "Write File" activity is correct as well the server name in bath file is correct as well the location of ftp.exe program on your machine. Since I sued the Windows XP, in that it is located under C:/windows/system32 probably on 2000 it is under C:/winnt/system32.