Michael: here are some recipes for homemade yogurt from the TKL archives. There are more if you search for "homemade yogurt" or "frozen yogurt"
Hope these help!
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YOGURT
8 c. water
3 1/4 c. powdered milk
1 tsp. plain gelatin in 2 tablespoons water
1/4 c. plain yogurt ( Make sure it contains a live culture.)
Mix milk and water. Heat to 105 degrees. Remove half of milk, heat to almost boiling. Add softened gelatin. Stir well then add the rest of the
milk. Stir in the plain yogurt. Cover with plastic wrap. Place in oven
with the light on. Check in 6 hours. If it's very thick (almost like Jello)
take out and store in refrigerator. Let stand 12 hours in refrigerator. Let
stand 12 hours in refrigerator before adding concentrated orange juice
or fresh fruit for serving.
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YOGURT CREAM CHEESE

Make a strainer with 3 to 4 layers of cheese cloth over a wide mouth
quart jar and rubber band. Put a pint of yogurt into the cheese cloth.
Wrage the whole thing in a plastic bag and let it drain for 24 hours in
the refrigerator. You can use this the same as any cream cheese-not
fat. Makes about 8 ounces.
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YOGURT
1 1/4 c. instant dry milk powder
1 1/4 c. non-instant dry milk
7 c. warm water
4 whole grain saccharin, dissolved in sm. amount of the warm water
1 tbsp. vanilla
1/3 c. yogurt live culture
(Yogurt has a slightly better flavor if some non-instant dry milk is
used. This can usually be purchased at a health food store. If not
available, use total of 3 cups instant dry milk powder. Yogurt culture is
simply plain commercial yogurt which you buy to eat.) Mix all
ingredients together thoroughly and pour into 2 quart jars. Place in
oven and keep temperature between 110 to 120 degrees until yogurt is
set, 2 to 3 hours. Do not disturb during this time. Chill immediately
when set so mixture does not become too sour or separate. Crushed
fruit may be strained into the yogurt mixture before it sets, but most
people like to add the fruit at serving time. Be sure to save 1/3 cup to
use for culture for your next batch. In several months you may need to
purchase a new culture if yogurt begins to get more strong and acidic.
(*To keep oven at correct temperature of 110 to 120 degrees, you can
turn it on and off for a short time occasionally. If the oven is small, the
turned on oven light provides a good amount of heat. Some people
simply leave the mixture on the countertop overnight, but depending
on the weather it could set before morning and would not be
refrigerated at the proper time. It usually takes about 6 hours at room
temperature. Check each half hour after 2 hours to see if mixture is
set.) Yield 2 quarts.

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YOGURT
1/2 tsp. unflavored gelatin
1 tbsp. sugar
3 c. instant powdered milk
1 lg. can evaporated milk
3 heaping tbsp. commercial yogurt (with live cultures)
Soften gelatin in water. Then add enough boiling water to make one
cup. Add the sugar and let cool to room temperature. Preheat oven to
about 275 degrees (250-300 degrees). Mix the powdered milk with 3
cups of tepid water in a heat-proof 2 quart mixing bowl. Add the
evaporated milk and two more cups of tepid water; stir well. Add the
gelatin mixture and the commercial yogurt and stir very thoroughly.
Cover the bowl. Open the oven, close the oven door. TURN OVEN
OFF. Turn on the oven light. Leave overnight or about 12-14 hours.
Makes about 2 quarts. (This makes great frozen pops for children.
Just mix one cup yogurt with 1/4 cup concentrated fruit juice. Pour
into molds and freeze.)