Batch file help

[thegillion]

I need help making a batch that is a login with User name and password

@echo off
:top
set loginname=""
set loginpassword=""
rem~~~~~~~~~clear variables~~~~~~
cls
rem~~~~~~~~~User input~~~~~~~
echo Enter Name:
set /p loginname=
echo Enter Password:
set /p loginpassword=
rem~~~~~~~~~runs lookup batch file~~~~~~~
lookup %loginname% & ":" & %loginpassword%
pause
goto top

the code for lookup.bat is
@ECHO OFF
FIND "%1" passwords.zip
The zip file is really a text file

I forget the if command for looking up the login and login password.
If anyone can help that would be great