In my monthly budget planning app I have following forms:

Expense Category: [Category]

Expense Subcategory: Lookup [Category]; [Subcategory]

Expenses: Lookup Expense Category: [Category]; Dynamic Lookup [Subcategory], [Amount]; [Date]; [Month(Date)]

Budget: Lookup Expense Category: [Category]; Dynamic Lookup [Subcategory], [Amount]; [Month]

Now what I would really like to achieve is to build a classic report summarizing expenses by Subcategory + an info from Budget how much was budgeted for that Subcategory, grouped by month. 

Any help greatly appreciated.