Error with definition of #define

Projects Programming
6

I already made the change, but the error is still there, on line 8:

Here is the code:

unsigned long timeout_start;
unsigned long timeout_ms;

#define TIMEOUT_2000MS 2000
#define ERROR_TIMEOUT 1
#define TIMEOUT_START { timeout_start = millis(); }
#define TIMEOUT_CHECK {
if ( (millis() - timeout_start) > timeout_ms )
  return ERROR_TIMEOUT;
}

void setup() {
  Serial.begin(115200);
  timeout_ms = TIMEOUT_2000MS;
  TIMEOUT_START
  while (!Serial.available() && TIMEOUT_CHECK) {
    delay(1);
  }
}

void loop() {
}

Here is the error message:

sketch_nov04a:8:1: error: expected unqualified-id before 'if'
if ( (millis() - timeout_start) > timeout_ms )

sketch_nov04a:10:1: error: expected declaration before '}' token

}
exit status 1
expected unqualified-id before 'if'