Lock/Unlock Cells Based On Criteria From Validation Lists

I'm looking for a solution to a problem and from what I've read in the forums so far, this is the place to come. I first want to say that I have tried to solve the problem by using guidance from other similar threads and adapt those answers to my needs, but as my understanding of VBA is non-existent this was somewhat difficult. I don't want to post a repeat question and I hate wasting people's time if unnecessary, but I can't do this on my own.

That being said, here is the problem;

(I have attached a simplified copy of the worksheet I am working on for reference)

I would like to lock a particular cell in my spreadsheet based upon the selections made from two drop down validation lists (Cells “C4” & “D4”)

Essentially, if a correct choice is made in both, then the cell “E4” becomes unlocked for editing. If however, the correct selection is made in one list, but not the other, I need the cell “E4” to remain locked and a message to appear to prompt the user to correct their mistake.

Furthermore, both the validation lists have a whole range of selections that are very similar but have subtle differences;

E.g.

"Soft Eye by Talurit"
"Soft Eye by Splice"

Is it possible to write a VBA code that performs a similar function to the =IF(ISNUMBER(SEARCH("**",))) formula, so that if any choice that contains the word "Soft" is selected from either or both lists then the cell “E4” becomes unlocked, but if the selection does not contain that word then the cell remains locked?

If anyone could provide a code to make this happen, I would be very grateful! But please explain how to do this, as the word “Soft” won’t be the only parameter and I may need to alter the code so I need to understand the principle behind it; For example, on the spreadsheet, if in the ‘Inboard End’ list a ‘Soft Eye’ is selected and on the ‘Outboard End List’ a ‘Soft Eye’ is selected then cell E4 is unlocked for editing. If in the ‘Inboard End’ list a ‘Soft Eye’ is selected and on the ‘Outboard End List’ a ‘Fused and Tapered’ is selected then cell E4 is unlocked for editing, but if in the ‘Inboard End’ list a ‘Soft Eye’ is selected and on the ‘Outboard End List’ a ‘Standard Eye’ is selected then cell E4 remains locked and an error message appears to alert the user that his/her choices are incorrect. If however, "Soft" is not selected in either list then cell E4 remains locked (it has to be selected in at least one of the two lists to allow editing).

This is a work in progress (not all the formulas that will eventually be used have been entered yet, so please excuse the untidiness of it all) and the choices are likely to change based on input from my colleagues, so I need to understand how the VBA works in order to alter it accordingly, but I don’t want to put any more work into this (it’s still in the early stages) if it isn’t possible to achieve these needs.