C＃Access数据库正在使用或权限失败

I'm using Access 2007 and C# to learn Databases. So far it's been rough but I've been able to handle things relatively well. What I need to do though is to query a my database table Accounts for the Amount of money a user has based on their pin. I've placed a button on the Windows Form I am using that will query the database on click. When I run/click the button as per normal I recieve the following error. I'm using Access 2007 and C# to learn Databases