I have been trying to update a text field in a form that will automatically generate a new number in a read only state when a user fills out the form. When the user completes the form and selects the submit button, the form will be attached to SharePoint List and the following user will open the form and the number field will be the number +1. I have used 'count(mynumber)' and the field returns 1, but when I close the form and re-open it, the field still displays 1 and never increases. When I use 'count(mynumber) + 1' the field returns 2 and also never updates. Finally, I used 'max(mynumber) +1' and it returns NaN. I have come to the conclusion that there is an array here, but don't know what I need to do, to fix this.
I have informed my manager of 'InfoPath 2010 Cookbook' so hopefully this will help, but I also took a gander as this following link, which was not easy to follow as I believe its for 2007 instead of 2010.
http://claytoncobb.wordpress.com/2009/06/15/auto-numbering-infopath-forms/
I am using SP 2010.