IF

Performs conditional processing in batch programs.
 
IF [NOT] ERRORLEVEL number command
IF [NOT] string1==string2 command
IF [NOT] EXIST filename command
IF [NOT] DEFINED variable command
 
  NOT               Specifies that Windows CE should carry out the command
                    only if the condition is false.
  ERRORLEVEL number Specifies a true condition if the last program run
                    returned an exit code equal to or greater than
                    the number specified.
  command           Specifies the command to carry out if the condition is met.
  string1==string2  Specifies a true condition if the specified text
                    strings match.
  EXIST filename    Specifies a true condition if the specified filename exists.
 
The DEFINED conditional works just like EXISTS except it takes
an environment variable name and returns true if the environment
variable is defined.