Dynamic drop down in Userform From Dynamic list

Hi good people!,

I am searching and found many tutorials on creating dependant, multi-level drop downs in a user form, from fixed source lists in a spreadsheet. Really what I am looking for is to create multi-level dependant drop downs in a user form, with the difference that the first drop down in the user form, is sourced from a dynamic list on the sheet.
This is what I am trying to accomplish:
Rows 2 and down from columns A to E are populated as time goes by. column A being user, column B being timedate stamp, C is Company, D is Item and E is Cost. Sometimes an entry would have to be altered, not deleted, and mostly it is the cost figure that would need changing, so I am thinking to populate the fields in the user form starting with the company name, then the 2nd drop down must populate depending on this input, and the third drop down will change depending on the second input.. Using the picture:
drop down 1 displays AA,BB,CC,DD,EE. Selecting for example AA, will cause the second drop down to display aa,dd..Selecting aa will display 44 and 48n in the third drop down. In the 4th drop down which is on the user form, I want to input a cost figure, which then, when I click a command button, will find the row of which the company, and Item and cost match the fields in the user form, and change the cost figure of that record to the new cost figure which was input in the 4th text box.

The reason we cannot just let a user find the entry by doing a search manually, is because the sheet is password protected and nobody can select any cells.

I sincerely hope someone will be able to assist me. Thank you all very much!