Ive just checked on my favourite sql site -
www.sqlteam.com - a poster there quotes using errorlevel with ISQLW.exe
testing errorlevel can be odd - it returns 0 for ok, anything else means an error - you would test this with
if errorlevel 1 goto ErrorHandling
this means if errorlevel is 1 OR MORE process the error, it its 0, then it is ok and continues to the next line