Change scene.. and GetKey func.

I am facing a problem with GetKey(..) function. It's a little hard to explain, anyways I am trying.

1. Pressing Key 'A' down, so i can check if Key 'A' is pressed or not.

2. while Key 'A' being pressed, i am pressing Key 'B' as well. And I can get both keys are pressing using GetKey(..) function.

3. When I move to another scene, the function GetKey('A') doesn't work. Only GetKey('B') works. I think the problem is related to hardware of keyboard.

I need the Key 'A' to be being pressed always even though other keys are pressed or not. Is it possible with Unity3D?

I am really looking forward any ideas or links. Thanks in advance.