Yes, I did something similar years ago using Microsoft Word's spell checking.
I found a VB6 example here
] - but note that I did not download the source code and check it
There is a VB.NET example here
] (that does not require a download to view the code). It should still work with VB6 (if you really must use VB6)
The highlighting etc was obviously within the VB6 code. I found an example of that here