Ok here goes
Set up Printer Template, mine is called OpenDrawer, include in the header the code to open the cash draw.
Set up a Print Job and map the OpenDrawer template
Add Action, named OpenDraw, Action Type>Execute Print Job. Enter Print Job name in Parameters section
Create two rules, first one Event Name>Work Period Started. Add OpenDraw to Actions, you dont need to add any details on other rules unless you want to restrict the OpenDraw to certain users/terminals. Second rule Event Name>Work Period Ended, also do the same as first rule.
Now Cash Drawer will fire whenever work period started or ended.