C# Signature:

[DllImport("kernel32.dll")]
public static extern IntPtr OpenProcess(
     ProcessAccessFlags processAccess,
     bool bInheritHandle,
     int processId
);
public static IntPtr OpenProcess(Process proc, ProcessAccessFlags flags)
{
     return OpenProcess(flags, false, proc.Id);
}

VB.NET Signature:

<DllImport("kernel32.dll")> _
Public Shared Function OpenProcess(processAccess As ProcessAccessFlags, bInheritHandle As Boolean, processId As Integer) As IntPtr
End Function

<DllImport("kernel32.dll")> _
Public Function OpenProcess(processAccess As Integer, bInheritHandle As Boolean, processId As Integer) As IntPtr
End Function

User-Defined Types:

    [Flags]
    public enum ProcessAccessFlags : uint
    {
        All = 0x001F0FFF,
        Terminate = 0x00000001,
        CreateThread = 0x00000002,
        VirtualMemoryOperation = 0x00000008,
        VirtualMemoryRead = 0x00000010,
        VirtualMemoryWrite = 0x00000020,
        DuplicateHandle = 0x00000040,
        CreateProcess = 0x000000080,
        SetQuota = 0x00000100,
        SetInformation = 0x00000200,
        QueryInformation = 0x00000400,
        QueryLimitedInformation = 0x00001000,
        Synchronize = 0x00100000
    }

Notes:

See also CloseHandle,