Compare The length of two string variables inside an Expression task in SSIS
I found the answer
I Created a variable @[User::Process] with Boolean data type and
I changed the Expression to this 

@[User::Process] = (DT_BOOL)((DT_I4) LEN( @[User::FileFormat] )==LEN( @[User::ExcelName] ) ? 1: 0)


And Changed the precedence constraint of the expression task to This