Help:Computer Timer MODIFICATION

Good day guys,

i need help modding a regular allan computer timer(or any other timer) (hulog hulog piso/singko)


i want to modify it so that (for example) 1 coin will activate a 10 minute countdown timer,

BUT

when I insert another coin, the time will not be extended but will reset for another 10 min countdown.


EXAMPLE
1. I insert 1 coin, I get 10 mins of time,
2. If I insert another coin anytime , the timer is reset again for 10 minutes.

OR TELL ME IF THERE IS SOMEBODY WHO CAN DO THIS FOR A MINIMAL FEE.

SALAMAT