I have IF(D2="PLUMBER","x","") in cell E2, for example.
I need x to refer to a range of cells in another sheet so that if PLUMBER is selected, E2 will show a drop-down menu (Data Validation option in Google Spreadsheet).
Also, I need to incorporate other possibilities too. For example, D2 could be REAL ESTATE AGENTS and then I would need a list of agents in E2 upon it's selection. In other words, D2 will be a drop-down menu as well.