reset number on year change

I am using the following formula to increase the 4 rightmost numbers of the myfield

to the next multiple of 10

2014-1100 . Next number is 2014-1110

number(substring(myfield; 6; 4)) - (number(substring(myfield; 6; 4)) mod 10) + 10

It is working well, but i would like it to reset the right most 4 numbers to 0000 when the year changes, i.e when 2015, then it should start 2015-0000

Thanks