Mac Quickbooks and Payroll

I've been using quickbooks for mac. I've been doing my payroll manually via a excel file to save money and because my employees vary from none to 5 or 6 from week to week based on my needs. Most of the time I only have 1 or 2 people working for me part-time. I haven't been entering anything for labor burden and would like to do that and would like it to show up as a job specific cost. How do I do this? Currently, I just post the cost to the job and then witholdings to separate witholdings accounts.

For example:
Person A works 10 hours at 10/hr. I write a check and select the item framing labor at a total cost of $100 and select the associated job. I then select on the expense tab the different sub-accounts for medicare, social security, federal tax withheld, and state tax withheld but don't tie them to a job or the would be negative numbers. Beyond that, I haven't entered anything and know that doesn't accurately show what I as the employer am responsible for and doesn't tie the labor burden to jobs. How do I do this in quickbooks for mac?