Tri-fold brochure template

[flips]

Hi!
I am about to make a simple tri-fold A4 brochure. I was about to do it in Pages, which has pre-defined templates for this, but I much prefer Nisus, so I think I will make it there.

But I am a little unsure of how to get it correct. I need to split the landscape A4 page in 3. But if I just make three columns, it will not be entirely correct, as the page margins will make it a little weird (skew the middle part, or how you would say it).

So, does anyone have a pre-made template to share, or tip on how I could do this?

[Hamid]

Try this template.

[flips]

Thanks! But I guess this will try to print outside the printer margins(?), and I do want some margins on each "third-part-page".
I guess doing the math is the deal. Like, if I want a 14 mm (or 12 or 13 or something) margin on each page-part. What would have to be the Width and Gutter for each of the three columns(?) ...

(I did make one that worked good enough for now, but it's not entirely correct, so I guess I will have to fine-tune it later ...)
For now I used page margins of 1.4 cm and column width of 7.97 cm and gutter of 1.4 cm, since this was just for printing 40 copies and handing out, it's good enough, but it would be nice to make a template that would work for professional prints and accurate folding.