thx Adrew, in deed my idea wasn't to connect to the FX display but just connected the counter in parallel with with its +/- buttons
(ahh it's very difficult for me to explain it in English

) it should be in this way
The Pandora already have 3 wire coming out that I've soldered to the PCB (SMD so it was very hard!), one "common", one for program-up and one for down, they are connected to 2 pushbuttons, so I can still push the +/- button already present on the Pandora or I can push my new 2 pushbuttons. My idea was to make a counter able to count up and down from 0 to 9, connect it in parallel with my added 2 pushbuttons so when I push the + or - (either on the FX or my new ones) the display change the numbers. I know I'll have problem when I switch off the power as the fx will remain on the program chosen and the counter will (probably) reset to 0, but I can live with that.
Anyway I saw now different IC I an use, like CD4510 and CD4511, if I understand them one is counting up or down and the other one is driving the 7-segment display, still need to understand how the whole thing should work, I'll keep on trying though
I've found on Internet some up/down counter like the "9 Second Digital Readout Countdown Timer" on this link (towards the end of the page)
http://ourworld.compuserve.com/homepages/Bill_Bowden/page2.htm#delay10.gifbut they are all "automatic", so driven by a 555 or something else, while I need it to be manual.
May be I've found a kit that will do this, is an old kit of an electronic paper of 7/8 years ago, I'm just waiting the sellers to reply to my request about the availability of the kit.
Still I would like to do it DIY like the whole pedalboard I'm building!
Thx again Andrew for your intereset in this.
Ciao
Armando