New reader that use read two files using two already existing readers

my simulation results are are divided in two different kind of files.
On one side I have OpenFOAM results and on the some .vtm files.
Right now I have to load the two sets of file independently and everything works fine.
I was wondering if it was possible, to create a reader, of a file .abc (in a known relative position with respect to the .foam and the .vtm), that allow me to load the two file at once.
Every suggestion will be appreciated.

A custom filter should do the trick:

Hello Mathieu,
thanks for the answer.
Maybe I did not explain myself well or I do not understand how to proceed.
Because at this point, I am not able to load the, so I am not sure how to go further and make then read the other two files.
Thanks again for all the help !

There is no alembic (.abc) reader in ParaView, but what does this have to do with reading two files ?

Thanks again. Using .abc as a example was not the best of ideas.
The output of my simulation is divided in two folders, one containing openfoam data and the other containing vtk data.
What I would like is to make a reader that read a file.principal which automatically load in paraview the .foam file and the vtk file.
Thanks and sorry if I was not clear in my questions.

To read a new format, you need to create a plugin, the simplest way is to use python.

See this answer by @utkarsh.ayachit :