Cascading/dependent combo boxes

I have a set of data, in the dynamic range A1:AE and whatever the last row is. Row 1 contains headings.
I have 2 comboxes; (the yellow highlighted columns)
1. cbo_DL (Column AF) (Columns AC and AD joined)
2. cbo_DLS (Column AG) (Columns AC, AD and AE joined)

I select a value from either combobox and the related values are displayed in a listbox.

Basically what I would like to do is have 3 comboboxes
1. cbo_DC (Col AC) (column coloured red)
2. cbo_LP (Col AD) (column coloured orange)
3. cbo_Ses (Col AE) (column coloured green) (will always be a value of in the range 1 to 10)

I select a value in the first combobox (cbo_DC) which then limits my choices for the 2nd comboxbox (cbo_LP) which then limits my choices for the 3rd combobox (cbo_Ses). Like filtering the data first on Column AC, then Column AD, then Column AE.
I have searched for a solution but I have only found references to dependent comboboxes/cascading comboxes that are not based on a data set.

Columns AK, AL, AM contain the unique values for each of Columns AC, AD and AE.
These unique values will NOT always be the same except for column AM, which will always be a number from 1 to 10.
I believe I need to fill the first combo box, then use 'change event' to fill the other 2 combo boxes to accomplish what I need.


I have attached a sample workbook.
Any assistance would be appreciated.