Problem regarding enum

[hoganlai2006]

Recently I have come across with a problem with enum. I have defined an enum as follows:

private void btnViewNumber_Click(object sender, EventArgs e)
{
if (machine.UpdateScreen(InventoryStockStateMachine.v iewNumber))
{
label1.Text = NupNumber.Value.ToString();
}
}

#region States

public enum InventoryStockStateMachine
{
viewNumber
};

#endregion

I have defined a public method UpdateScreen in statemachine class and make it accessible from the main class.

using System;
using System.Collections.Generic;
using System.Text;

namespace testingDeviceBattery.StateMachine
{
public class StateMachine
{
public bool UpdateScreen(InventoryStockStateMachine stateDef)
{
bool status = false;

if (stateDef == InventoryStockStateMachine.viewNumber)
{
status = true;
}

return status;
}

#region States

public enum InventoryStockStateMachine
{
viewNumber
};

#endregion

}
}

But the compiler complains with the following error messages:
Inconsistent accessibility: parameter type 'testingDeviceBattery.StateMachine.StateMachine.In ventoryStockStateMachine' is less accessible than method 'testingDeviceBattery.StateMachine.StateMachine.Up dateScreen(testingDeviceBattery.StateMachine.State Machine.InventoryStockStateMachine)'

Does anyone know how to fix it..
Thanks!!!!