I can't substitute players in cup mode in PES 6...

[Ernesto Lee]

hello guys I tried to play the EURO2008 in PES 6 in the cup mode, but during the game when I tried to do the most simple operation of the game it denied me, it doesn't allow me to substitute players...
What shall I do?
thanx

 

[Ernesto Lee]

I guess nobody will answer here isnt it?