VST EXPRESSION MAPPING PROBLEM

Hello from Greece.
I 'm working some expression maps in Cubase 5 on a friends pc and i got this weird problem.
When a library has keyswitches below C0 ,cubase doesn’t leave me to assign anything below C0.
For example: Straweberry Electric Guitar has keyswitches starting from A-1.When i try in expression maps to assign the keyswitches ,Cubase starts to assign from C0 and above.
How can i fix this???
Thanks in advance

nobody to say a solution???