MathCAD 15 - E-books installation directory

Hi everyone

Is it possible to install (permanently) E-books (like for example one of my favorites "dynamassist" or "Images") in a directory different from the /Handbook directory, where I have no write rights?

I have seen, I can open an E-book wherever I want, but the ones stored in /Handbook remain available also after closing and starting MathCAD again.  

Thanks a lot!

Best regards

Claudio