Disc Numbers

I am hoping someone can help with this. The following is the expression I use to rename most of my files. The problem is that I use a "1/2" (disc one of two) format and the following expression looks like:

$validate(%artist% - %album% - %discnumber%$num(%track%,2) - %title%,-)
Artist - Album- disc 1 - 1201 - Title

I need it to ignore the "/2" and only use the first number of the disc field ONLY when it is present.

Any ideas?

Handle DISCNUMBER tag field content the same way as you did it with the TRACK tag field content, e. g. [$num(%discnumber%,1)]. The square brackets do their task "when it is present".

Advising: Read the manual and search the forum ... and you will find answers without waiting for an answer, even for this problem.

DD.20100302.0820.CET

I honestly tried to find something to help me as it seems so simple. The funny thing is I was looking for help on a specific task a weeks ago and couldn't find a thing, then when I was looking for something else I ended up finding all kinds of stuff I couldn't before. I think that I'm just not used to the "expression terminology" or something... thanks for you help.