Potential Divider

You would be better getting a relay with a 220v ac coil.
But....

If you put a diode and a resistor in series with the 220v ac you may find the relay will buzz. But if you insist on trying it then a rough calculation would be something like this...

R= V/I you want to drop about 210 volt (but oh dear do we want peak volts? RMS whatever..or do we add a capacitor to stop the relay buzzing? Never mind let's press on regardless and see what we get.)
R= 210/ 0.3 well this is 700 ohms (680 is nearest common value)
Power dissipation is V²/R this would be approx 65watts...
Hmmm maybe you can now see why I said you'd be better off getting a relay with a 220v ac coil? mains relays are cheap and plentiful.
Del

He can also use a 60 W light bulb and it will also make visible the status of the relay...

For this amount of step-down voltage and power a resistive voltage divider is not going to be practical, cheap or electrically safe.

If you cannot use a 220V AC relay (inexpensive and easy to obtain) I would suggest either using a small inexpensive (and MUCH safer) transformer and regulator or zener voltage divider network or (if space is a problem AND you know what you are doing electrically) using a capacitor voltage divider network which eliminates the massive losses.

http://cr4.globalspec.com/comment/133640

http://en.wikipedia.org/wiki/Voltage_divider

http://en.wikipedia.org/wiki/Linear_regulator

For this application SERIOUSLY consider a small and inexpensive transformer as this will reduce power losses and electrocution hazards.

The question you ask is a sign that you are new to this type of thing.

It is an unsafe way to solve the problem.

So please, just buy a 240VAC relay, it'll be cheaper than buying appropriately sized resistors, diodes & capacitor.