Ruby,
In fact the best solition for your lat/ long issue is to make a formula field to concatenate the lat/ long together like 123-456. I think you have that already done.
In fact, a little known secret is that a formula in fact can be the Key field to a table. You just need to type in the API call by hand into your browser.
Just get to the table and after the ? Hand type
act=API_SetKeyField&fid=99
When 99 is the field ID number.
You can double check the syntax in the API help guide, but I think that is it. I would turn off App tokens when you do that or else you would need to supply one to make that change
Then you don�t need form rules to copy across a formula to a text key field!
