Highlighting single word in text string gone wrong

I have a problem when I want to only highlight certain words in a text string where it does not highlight all of the words in the string.

I'm using this VBA code, which I found in this forum but found out that the words needs to be in the correct order for the words to be highlighted.

For instance if a cell contains the text "this is a test"
And I want to highlight "test" and "is" - if I write it in this order in the code it will only highlight "test"

Can anybody help?