Dependent dropdowns for Spreadsheet

Hi,

I was trying to create multiple dependent dropdowns in Spreadsheet, but it isn't working.
1) Column E dependent on Column D and
2) Column D is dependent on Column C
3) Column I dependent on Column H

Attached file for reference. Please note that the data tables are in sheet 2 of the file.

It will be nice to have some advice from anyone of you.

Thanks
Arnab

Hi Richard, thanks for your response. I did go through the link shared by you and tried it out. However, this is does not work when the file is uploaded in Google drive and opened as Spreadsheet.
Not sure if dependent dropdown is possible in spreadsheet.

Thanks again.