Getting “java.lang.NoClassDefFoundError” on running with javaagent- BCEL

I am trying to instrument a jar file (main.jar) with javaagent.jar using BCEL. basically where ever I find any aload in bytecode, I m trying to insert a function call to a static function called Fun() in class "someclass" using

if (opcode instanceof aload) {
iFactory.createInvoke("someclass", "fun", Type.VOID, new Type[]{}, Constants.INVOKESTATIC);
my "someclass" class reside in javaagent.jar

on executing

java -javaagent:javaagent.jar -jar main.jar
or

java -javaagent:javaagent.jar -jar main.jar javaagent.jar
or (I created a separate jar for my "someclass" called someclasscontained.jar)

java -cp someclasscontained.jar -javaagent:javaagent.jar -jar main.jar
I am getting

Exception in thread "main" java.lang.NoClassDefFoundError: someclass
error. i tried with -bootclasspath/p option but still not working. does anyone has any clue?

(1) all jar resides in same folder 2)checked all silly mistakes 3) used full qualified classname