Dependent dropdown with option to add new in both defendant columns

[pratik_modi]

I have a table->

Expense Type	Expense For
Mechanical	JCB 4DX
Mechanical	JCB 3DX Extra
Stationary	Pen
Stationary	Register
Survey	Measurment tape 5 Mtr
Survey	Measurment tape 15 Mtr
Survey	Measurement tape 30 Mtr
Mess	Food Parcel
Mess	Tea/Snacks
Electrical	Wire/Cable
Electrical	Bulb
Electrical	Motor Winding

In another table, vouchers details having both the columns of Expense Type and Expense For.
Want to create dependent dropdown list in both columns but also to have option of add new record in both columns.
When Adding in Expense Type- it should ask for only Expense Type Value.
When Adding in Expense For- it should ask for only “Expense For” Value which is of the Expense Type as selected in the Main Form.