I’d use a timer to call a function. The timer is because you want the LED widget to blink, and the frequency will be dictated by the timer.
You’ll need a global variable to track the state of the LED widget, so you can flip it.
You’ll also need a global variable to check the state of the relay, and only do the flipping if the relay is on.
The pseudocode for the timed function would be something like this…
if(LED_state = 255)
blynk.virttualWrite (LED_Vpin, 0);
LED_state = 0;
blynk.virttualWrite (LED_Vpin, 255);
LED_state = 255;
You’ll also want to turn the LED widget off and set LED_state to 0 when you turn your relay off, but this would be done in the function where you relay on/off via a virtual pin…