You can do this with a macro. Select the cell to contain the list and invoke the macro.
In the macro, examine the value of the cell to the left. Based on that value, insert the appropriate drop down list in the selected cell.
You can generate sample code to insert the drop down list by recording a macro while you manually create such a list. Copy the code from this recorded macro to your processing macro as many times as needed, manually tweaking the code each time to generate the actual drop down list desired.