I suspect that this is another of the limitations that are inherent with the SplitForm view.
Bottom line is that setting the Column Order is only available with Datasheet View Forms. Only workaround I can think of would be to use a separate Datasheet View Form, along with a Single View Form, to emulate a SplitForm. If you search here, or google, you should find some help with this, as it's been addressed heavily by the Access development community.
Here's a site with one example to download:
https://www.access-programmers.co.uk...d.php?t=284896
Linq ;0)>
The problem with making anything foolproof...is that fools are so darn ingenious!
All posts/responses based on Access 2003/2007