//This is a replacement for Cursor.Position in WinForms
[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern bool SetCursorPos(int x, int y);

[System.Runtime.InteropServices.DllImport("user32.dll")]
public static extern void mouse_event(int dwFlags, int dx, int dy, int cButtons, int dwExtraInfo);

public const int MOUSEEVENTF_LEFTDOWN = 0x02;
public const int MOUSEEVENTF_LEFTUP = 0x04;

//This simulates a left mouse click
public static void LeftMouseClick(int xpos, int ypos)
{
    SetCursorPos(xpos, ypos);
    mouse_event(MOUSEEVENTF_LEFTDOWN, xpos, ypos, 0, 0);
    mouse_event(MOUSEEVENTF_LEFTUP, xpos, ypos, 0, 0);
}