This is how I would do this.
When recording the bill, put the $800.00 to the COGS or Expense item and put the $200.00 into a bank account (Called Commissions). When you disperse the $200.00 as commissions, you simply transfer the amount from the Commissions Bank to your Actual Bank and then pay the commissions like you normally do. This will show the commission amount on your balance sheet as cash until it is dispersed.
If you want it to show as a liability on the Balance sheet, just set up a liability account instead of a bank account. The process will be the same.
Contact me if this is not clear or you need further explanation.