Conditional Formatting in grids: Can I make a cell turn red after entering a value in another cell?

Summary:

Can Forms 2.0's Format/Validation Rule Builder apply conditional formatting to Cell 1, changing its color to red when Cell 2 is populated, if Cell 1 is initially blank, to indicate it's now a required field?

Content (please ensure you mask any confidential information):

In Navigator/Create and Manage/Forms/Layout/Format/Validation Rules - Format/Validation Rule Builder, we want to create a conditional formatting rule that makes Cell 1 appear blank and editable on initial form load, but when a value is entered in Cell 2, Cell 1 turns red to remind users that it is now a required field and to enter a value in Cell 1 before saving the form.