Hi Scott,

Set the Focus to your ComboBox and send the ENTER keyboard event using
keybd_event. Here's some sample code for sending keyboard events

[DllImport("coredll.dll")]
static extern void keybd_event(byte bVk, byte bScan, int dwFlags, int
dwExtraInfo);

const int KEYEVENTF_KEYPRESS = 0x0000;
const int KEYEVENTF_KEYUP = 0x0002;

void SendKey(System.Windows.Forms.Keys key) {
 keybd_event((byte)key, 0, KEYEVENTF_KEYPRESS, 0); // key press
 keybd_event((byte)key, 0, KEYEVENTF_KEYUP, 0); // key release
(KEYEVENTF_KEYUP)
}