Series Of Dependent Comboboxes In Userform That Show Unique Values Of Dynamic Tables

This example workbook contains a datatable, which is inputted via a userform. The datatable has 4 columns: Date, Invoice no., Loads, Tonnage. This table is dynamic, as a new row gets entered each time data is entered in the userform. A different userform (the one in the example) has comboboxes which refer to the data in the table. This userform asks the user for the Date, Invoice no., Loads and Tonnage. I want to use comboboxes so that they will advise the input based on the users previous input.

The first combobox asks the user for a data, and should contain a list of all the unique dates that are stored in the table. When the first combobox is inputted, the list for the second combobox will change. The list of the second combobox should be a list of unique invoice numbers, based on the date that has already been entered. The 3rd and the 4th combobox should also show a list of unique values, based on the previously entered date and invoice no.

Example: The first combobox should advise the dates: 4-Nov-14 and 15-Nov-14. User chooses 4-Nov --> second combobox should advise unique invoice numbers based on chosen date: 1252 and 1311. User chooses 1152 --> 3rd combobox should advise unique values based on previous values: 3, 8 and 7. 4th combobox: 57, 23 and 47.