One technique would be to put code in the DocReady event to evaluate the form state.
See which subform should be acted on, and determine which fields on the form should be opened for edit.
You can use the layout ready event of a subform that contains a signature field to check if the specific fields for that signature meet your validations
- Set the access of the appropriate signature field to 'open' - if they are not,set it as 'protected'.
You can also evaluate the signature fields to check it they contain a valid signature to indicate which subform should be opened for edit.