I want to set the stop-loss and take-profit as a function of the current spread. They should be variable and not constant. The stop-loss and take-profit should be 10 times the current spread. Could you please tell me how to do it? Also plz tell me how to fetch the current spread value. Thanks.

Consider the following approach:

ITick tick = history.getLastTick(Instrument.EURUSD);
double stread10Times = (tick.getBid() - tick.getAsk()) * 10;

See:
https://www.dukascopy.com/wiki/#History_ticks/Last_tick

On this page, I saw the following rules for setting stop-loss for an existing order :

https://www.dukascopy.com/wiki/#Set_Stop_Loss_price

In order to set Stop Loss price the following conditions must be met:

- Stop Loss price must be divisible by 0.5 pips, otherwise the order will be rejected.
- One can not set Stop Loss price more than once within a second.

I want to setup stop-loss as a function of spread whose value will be constantly fluctuating. Will these rules come into picture in my case or do they just apply for an existing order?

Yes you have to conform with them.
For rounding sl price to 0.1 pips see:
https://www.dukascopy.com/wiki/#Rounding_prices
For 1 second restriction adhering example see the if condition just after the onTick:
https://www.dukascopy.com/wiki/#Set_Stop_Loss_price/Keep_track_on_Stop_Loss_changes