Three fruit marmalade

Hi, does anyone have an easy recipe for marmalade made with grapefruit, oranges and lemons? I have lost my Mum's recipe and am hoping someone has a similar one. Thnx.

Magenta's recipe
I made 4 large Vegemite jars of marmalade using my version an Alison Holst recipe. I have lots of limes so I used those. I guess you could use grapefruit if you wanted. I usually peel the citrus using a potato peeler and then cut up fine. Then I squeeze out the juice and chop up the remainder very finely. Alison Holst says just use the food processor. I dont find this very satisfactory and for a small amount just do it by hand. Anyway the recipe I used was 5 limes ( about 500g I guess) 1 litre water, 1/2 pkt jam setting mix, 11/2 tsp citric acid, 1kg sugar. Boil up the fruit and water for about 10 mins. Add the jam setting mix and citric acid and boil 10 minutes longer, stirring frequently. Add the sugar and return the mixture stirring until sugar dissolves. Boil briskly until skin forms when a small amount is placed on a cold saucer. Place in hot sterilized jars. You could use a couple of grapefruit to one lemon I would guess. In the past when using grapefruit for marmalade, I have soaked the cut citrus over night in the water as it seems to soften the skin up a bit. Hope you can make sense of this!

Thanks noonesgirl, will give it a go... I've got grapefruit, oranges and lemons coming out of my ears! !