Something to remember is that be default .bat and .cmd scripts do not process all the variable updates, or expansion, immediately. To use variable that are updated or created inside a loop for instance you must have Variable Expansion enabled.

A quick check to see if  variable expansion is enable in your command prompt is to run this:

If Variable Expansion is ON you will see:
c:\> echo !errorlevel!
0

If expansion is OFF you get:
c:\> echo !errorlevel!
!errorlevel!

When launching cmd.exe from a prompt; Command-line; Run…; or Search programs and files you can specify the /V:ON parameter to enable expansion.

Within a bat/cmd file variable expansion can be controlled through the SETLOCAL [ENABLEDELAYEDEXPANSION | DISABLEDELAYEDEXPANSION] statement.

Turn on variable expansion (delayed) and you will not be sorry.

–Mike