Passing commands to cmake?

[a]

Hello I am trying to use macports to install a package, SDRAngel.
The software installs perfectly using the ports, thanks to the maintainer.
However, I would like to rebuild it to use a plugin library which is
not part of the main package.

The documentation says:
"For mbelibsupport you will need to specify the -DUSE_MBELIB=ON
directive on the cmake command line and you will need to have mbelib
installed in your system."

I believe I have compiled the library to the correct location, but now
I am unsure how to tell macports to use this command when building the
package.

I am very new to this and I do not even know what to search for this,
I apologize if this is a simple common problem. Thanks!

-M