Clarification:
I see that I too hastily posted the question. 0,0,0 would be Earth.
The
figure for 'x' would need to be the distance from Earth, with y and z
being
taken from RA and DEC...is that right?

If we use the stars of Orions belt as an example, can you help me put
them
to x,y,z?

Alnitak: 400ly, RA 05 40 45.5, DEC -01 56 34
Alnilam: 1340ly, RA 05 36 12.7, DEC -01 12 07
Mintaka: 600ly, RA 05 32 00.3, DEC -00 17 57