Yes as long as you've found the correct string its ok to just change E1 to E3.

"A picture paints a 1000 words":

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As you can see above i've already made it. But it's good you want to do it yourself, so 'practice Grasshopper'. It's late here, i'm old and tired and had a bad day so i'm having a big Scotch [single malt, don't scoff] and going to bed.
Post again if you need help and i'll attached the kit for you to put on the card and flash with [but tomorrow ].