Hi pruppert,
In your
unprotected document, press Cmd-F11 (I think) to access the vba editor. On the left side of the screen you'll see a project with your document's name. Expand that so you can see a module named 'ThisDocument'. Double-click on 'ThisDocument', then enter the following code on the main panel:
Code:
Sub Collapse()
Selection.Collapse
End Sub
Exit the vba editor (eg Cmd-F11) and return to your document. Select a formfield and, from the Developer tab, choose 'Properties. A dialogue box will pop up. Under 'Run macro on', one of the listed properties will be 'Entry'. Use the dropdown there to select 'Collapse'. Protect the document for forms. Now, whenever the formfield is selected via tabbing, the selection will collapse to the start. If you select the formfield via the mouse, the selection will collapse to the insertion point.