Calling the constructor of the base class after some other instructions in C++

As far as I know it is not possible to call the constructor of the base class. The only way I know is this:

MyClass::MyClass(/* args */) : Base(/* args */)
{
   // ...
}

but this would invoke the constructor at the beginning. Is there any way to call it somewhere else in the constructor? Something like this:

MyClass::MyClass(/* args */)
{
   // ... instructions
   Base::Base(/* args */);
   // ... other_instructions
}

According to this What are the rules for calling the superclass constructor? question I understand there is no way but I read here and I guessed it was possible, but if I try I get:

error: invalid use of 'class Base'.

Am I doing something wrong? Is it possible to do this some way or is there any other possible solution to this need?

Thanks!

EDIT: I understand I forgot a key point: the base class is part of a framework, and therefore it would be good not to have to modify it, if possible.