Budget Periods and Accounts

To be able to choose the exact period of budgets: I have a budget for groceries every month: the first it’s from 01st to 14th (so choosing 2 weeks is fine) but the second is from 15th to the last day of the month, but if I choose 2 weeks it doesn’t suit me as it always ends on the 28th. Also, I’d like to select which accounts that budget should use, as I have several accounts set up but only one or two should be considered on the budget.