Night shift allowance

My client wants to give employees 10 Rs for every night they work as night shift allowance. How to accomplish this.

I was trying it with one rule

000010 D OUTWPSHIFT

000020 ****

000030 SS-C AMT=10 ADDWT 8000

but this rule is not working. I have inserted it in INAL before x023. Do i place it in XT00 and if yes where to place. Please guide.