Hi Sophia,
You can create a rule and call the WT from cumulation table (AMT=CYXXXX), where CY refers to cumulated yearly amount from the CRT table and xxxx is the wagetype. THen to convert the amount to positive, you can multiply the amount with -1 (AMT*-1) which will convert the amount to positive and then add the amount to the new WT (ADDWT YYYY) where YYYY is the new wagetype.
Regards,
Manj