Hi-Ya, Patricia!
As my pal, Mickey Mouse, would say, "It's swell to hear from you!"
Disney Dining Plan details can be a bit tricky sometimes, so I'm happy to navigate you through them like a Disney's Magical Express motorcoach on those complicated Florida highways. Everyone buckled up and ready? Away we go...
While you aren't able to split the cost of a meal between dining credits and out of pocket like the example you gave, luckily, there is another "detour" you can take to get to the same "destination." You are able to split payment methods per person instead of entree. For example, if two of you are dining at a two table service dining credit location, but you only want to spend two dining entitlements, rather than four, you could have one person use their two dining service credits and pay out of pocket for the other Guest.
I hope this information helps in "mapping out" your dining adventure, Patricia, but please let us know if you need any other assistance.
Magical Wishes,
Lauren