[pstricks] Tweak a PSTRICKS source file. Ask for help!

[Jorge Luis Llanio]

Dear All,

In the picture that follows, I want the central atom in the triatomic A
molecule to be positioned lying  along the Z-axis, so I use

\rput(0,1){\MyBall[lightgray]} (see the PSTRICKS source)

but I want it to "eclipse" the Z-axis; I mean, I don't want to see the
Z-axis passing through my ball \MyBall[lightgray], the Z-axis should be
interrupted

Any suggestions? Thank you very much in advance,

Jorge Luis