WIN32_CTL_INPUT_STATUS

Setting this variable to the default of TRUE (ON, YES, 1) causes ACCEPT...FROM INPUT STATUS to return a non-zero status if data is available in a control. If set to FALSE (OFF, NO, 0), then the data in the control does not affect the status returned by ACCEPT...FROM INPUT STATUS.

This variable is only available in the Windows runtime and is not available to the thin client.