Automatically punctuate a formula that lists text with commas and, fullstop.

[ddee]

I was very kindly helped with some formulas a few weeks ago to help me query a summary spreadsheet, I didn't finish the job then, but am trying to now. What I am trying to do is create a written report with the data coming from summary sheet queries. This will help me reduce user error cutting and pasting data.

What I would like to do is for the formula in k20 to return the text from each cell with a comma between each except for the last for which I would like an "and" before and a full stop after. That is make the text grammatically correct. So instead of k20 reading:

Test had a definite difference more than others for C. Vestibular Processing and E. Multisensory Processing and F. Oral Sensory Processing.

I would like it to read:

Test had a definite difference more than others for C. Vestibular Processing, E. Multisensory Processing and F. Oral Sensory Processing.

Is this possible?