Using Two Backgroundworker On Two Different Invisible Forms?

i'm using two backgroundworker on two different invisible forms.One bgworker starts to work before the second, it depends on the cpu usage calculated every minute.

When the second bgworker starts to work, an operation me.invoke is called to show a message, but when the code reachs the comand, the system give me this exception : impossible to call invoke or begininvoke method without a form handle.The me.invoke method is called during the dowork fase of the bgWorker.