a pkgbuild is a really simple file to read and you would only need to edit the version and that is about it.
Below is the ndiswrapper PKGBUILD for ndiswrapper .10(there are newer versions though) from Phrakture at the arch website. Copy everything and save it as PKGBUILD. I would make a dir /var/abs/local/ndiswrapper and save the PKGBUILD in there(you will have to save it, then move it as root) and do the same with the ndiswrapper file. cd into that directory and type as root "makepkg" without the quotes. after it is done type "pacman -A ndiswrapper<hit tab here>"(it should be again with out the quotes. then you will have ndiswrapper installed. If you want the newest version, change the pkgver line from 0.10 to 1.6 and that should get you the latest and greatest ndiswrapper. good luck
pkgname=ndiswrapper
pkgver=0.10
pkgrel=1
pkgdesc="Module for NDIS (Windows Network Drivers) drivers supplied by vendors"
url="ndiswrapper.sourceforge.net"
depends=(wireless_tools)
source=(
http://optusnet.dl.sourceforge.net/s...e/ndiswrapper/$pkgname-$pkgver.tar.gz)
md5sums=()
build()
{
cd $startdir/src/$pkgname-$pkgver
make || return 1
#ndiswrapper provides some bunk makefile which installs to hardcoded paths
# we'll fix that here.... and manually install ourselves (thank god this is
# a small install)
pkgdir="${startdir}/pkg"
mkdir -p $pkgdir/lib/modules/`uname -r`/misc
install -m 644 driver/ndiswrapper.ko $pkgdir/lib/modules/`uname -r`/misc
/sbin/depmod -a
mkdir -p $pkgdir/sbin
mkdir -p $pkgdir/usr/sbin
install -m 755 utils/loadndisdriver $pkgdir/sbin
install -m 755 utils/ndiswrapper $pkgdir/usr/sbin
install -m 755 utils/ndiswrapper-buginfo $pkgdir/usr/sbin
mkdir -p $pkgdir/usr/man/man8
install -m 644 ndiswrapper.8 $pkgdir/usr/man/man8
}