Entering text in a locked cell

I have worksheet that contain values in column E and G and the total in column K. E and G are unlocked for manual input and column K contains the formula for the total and is locked. From time to time a certain row will not be applicable and before I started locking the cells in column K i would just put "not applicable". Now that it's lock I can't do that. My only option now is to put O in column E and G but I would rather put "not applicable" in column K. Is there a way around this. I was thinking of something along the line of a macro that would unlock the worksheet input the text and re lock it. The macro would have to lunch when a locked cell is selected or have a button that would launch the macro an would prompt for which cell the text would be entered. Is this possible.

This is very cool. One small thing. I put this in my workbook and no matter what sheet I'm on it inputs it in the first sheet. How do I modify the code so that it would unlock, insert and lock the sheet I'm on or I can make a macro for each sheet and have a button to launch the macro. If I do it this way what do I put instead of Sheets (1). I tried Sheets (Name of my sheet) but that didn't work.

That's exactly what I was looking for however for some reason I couldn't get it to work in my workbook. Probably because not every cell in column E and G are unlocked and not every cell in column K are locked. I tried erasing the column reference in the code and that seems to work. I also added my password because the worksheets are password protected. It seems to work beautifully across all worksheets. However there are 6 of the worksheet that this would apply too and all have different areas that are locked so will have to do more testing next week to make 100% sure it works everywhere but as of now it appears to work everywhere. This is how the code looks like now.

Thanks so much for this. Everyday I learn something new on excel and it never ceases to amaze me. This has already given my ideas for future applications. +1 for you

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Is there a way to change the code so that I would have to enter cell location and also enter the text to be displayed. Just ran across a scenario that I wanted to enter text other than not applicable.

That's perfect. Thanks again