Conditional Formatting - Grey Out and Lock A range based on a cell value in that range

HI Everyone,

I cant seem to find the code im looking for, i was hoping someone could help me.

Basically i have a sheet with a drop down menu by Account and when people select the account the costs of various activities are pulled across into the front sheet and multiplied out etc. I cant lock out the full row as columns further down the row may be valid.

What i would like to happen is if there is no cost for that activity then the range will be greyed out and locked.

I have attached the sheet i am working with to help with the solution.

Thanks