Is there a way to set an InfoPath attach control field to required after the form has been submitted.
Infopath doesnt allow validation rule for attachements. Below is a workaround.
•Create a text field to use for validating purpose (name it something like 'Attachment Validation').
•Place it on your form and remove the borders and shading. Open the field text box properties under the Display tab and set it to Read Only and set the default value to "Attachments"
•Place a validation rule on this field. The condition should be 'The Expression' and set it to count(../my:Attachments/attachmentURL) = 0
The expression basically counts the number of attachments and if it equals 0 then it will put the red dashed line around the word Attachment.