Search text string and return multiple results depending on content of text string

Country Task List_EXAMPLE.xlsx

Dear all, I have tried many variations of FIND ISERROR OR ISBLANK etc. etc. combinations to no avail.
Essentially, I need to search multiple text strings, and depending on the content, return another text string.
This is a list of items that our international office sends to multiple countries, they write down the countries affected in a column, eg “GB, DE, FR” or leave it blank if all countries are affected.
So if column B is blank, I need an “X” in column C to say – we need to action this item
If column B contains “GB” in a text string of countries, I need an “X” in column C as again we need to action this item.
If column B contains the text “all except” I need column C to say “CHECK!” as the Admin Assistant dealing with this week’s memo will need to manually check which counties are excluded (unless we can automate it to differentiate between say “all except DE, FR, ES, GB” meaning no “X” should be in column C, and “all except DE” meaning “GB” does need to action this item, so “X” should appear) Although I am content enough with a “CHECK!!” text flag to the secretary – I am struggling with this so the above may be a bit too far!!
Please find attached example spreadsheet that highlights what I want to accomplish.

Thanks in advance for your help.

I am not sure if this would work in Excel for MAC.

In D2:
=IF(ISNUMBER(SEARCH("all except",B2,1)),"CHECK!","X")