How can I call my set my callback function from an object?

Here is some code:

typedef void (*ACallBack)(int i, void* userData);

class SomeClass
{
private:
   ACallBack aCallBack;

public:
   void SetCallBack(ACallBack aCallBack, void* userData = NULL);
};

void SomeClass::SetCallBack(ACallBack aCallBack, void* userData)
{
   this->aCallBack = aCallBack;
}

class SomeOtherClass
{
private:
   SomeClass someClass;

public:
   void InitializeSomeClass();

private:
   void callBackMethod(int i, void* userData);
};

void SomeOtherClass::InitializeSomeClass()
{
   this->changeVariable = 10;

   this->someClass.SetCallBack(this->callBackMethod); // DOESN'T WORK
   this->someClass.UseCallBack();
}

void SomeOtherClass::callBackMethod(int i, void* userData)
{
}

void globalCallBack(int i, void* userData)
{
   int myInt = i;
}

int main()
{
   SomeClass sC;
   sC.SetCallBack(globalCallBack); //WORKS!!
}

Basically if I try to set my callback function in SomeOtherClass it doesn't work but when I set it globally in main it does. What am I missing here?