How to make a UMG text box writable in game

UE4 4.12.5

I can’t seem to find how to make a text box writable if it’s been set to read only in the Designer.
In the event graph I can get “Is Read Only” but it doesn’t look like I can set “Is Read Only”.

By default I want it to be read only.
If certain conditions are met in-game, then I want to disable Read Only (make it writable) temporarily.

Should I use “Is Enabled” instead to achieve what I’m after?

Thanks for any help.

Sorry.

Setting the text box’s Visibility to “Hit Test Invisible” when I want it read only,
and then Visible to make it writable achieved the effect I was after.

Only problem with approach is you can’t copy the text in the text box.