Prevent Deletion Of A Cell With No Cell Protection

I have a worksheet with multiple entry boxes in a row. Depending on the value in one row, another row will either yield the result from a formula, or remain blank, and this cell needs to be locked. I was able to do this by first putting the formula into the destination cell, and then using custom data validation that says the cell value = "". So this prevents anyone from typing in that cell, no matter if it yields the formula result or must stay blank. What it doesn't protect against is someone deleting the contents of the cell. The reason I don't want to protect the cell is because I want people to be able to highlight the whole row past that cell and delete it all at once. So either using Data Validation, a formula, or VB programming I need to not allow someone to do ANYTHING to that cell, even delete the contents, without locking the cell. Hopefully it can be done, thanks!

For example, if E17 = "X", then K17 = INPUT!$M$28*J17. If E17 <> "X" then K17 is blank. Either way, I don't want any typing or deleting of K17. This applies for range K17:K91, and corresponding E17:E91.