Click 3 times or 2 times

On frmExpenditure I have the following ComboBoxes:-

TransactionTypeID
ContractID
WorkOrderID (eg. maintenance work)

I am trying to think if there is a user-friendly way to enter data into only 2 of the comboboxes, instead of entering data into all 3?
Note: all the Tables have a Relationship.
Not all Expenditure will be related to a WorkOrder.

Currently, the User has to input 3 fields of data:-

1. Select the TransactionType (I expect there to be many WorkOrders)
2. Then select the ContractID.
3. And then, select the WorkOrderID (but ONLY IF the TransactionType is “WorkOrder”). This field should be left empty if it is not WorkOrder related).

I would appreciate any thoughts you have about if there is a way to only click 2 fields of data, like such:-

1. Select the TransactionType
2. If the Transaction Type is “WorkOrder” then input the WorkOrderID (and the ContractID automatically updates itself).
3. If the TransactionType is NOT “WorkOrder” then only need to input the ContractID.

I have attached a basic database to show the problem better.

Attached Files

Database WorkOrder.zip (87.8 KB)