Excel - Lock Cells based on value of another cell in row from a list and not use a value unless another value is used first

[NuCeritySherry]

I’m trying to create an attendance workbook with each sheet being the month, with multiple rows/column. I have created a drop down list to choose from on a different worksheet. What I need is the following; HVX and HVP can only be used if HV has been used in the cell before. If D is used then they are unable to enter anything else in the rest of the row. I’ve tried creating formulas for this but does not seem to work and also have tried Data Validation. My VBA is at beginner. If anyone could shed some light on how to accomplish this, I would appreciate this.