You may want to leverage the SYS:Message box form. It allows for confirmations. Here is a brief overview on how to do that:
1) Create a record with the Message text and Message Tag (unique identifier for your message).
2) Have your workflow open the SYS:Message Box form (the dialog view has yes/no buttons):
- Add your Message tag in the open window input mapping
- In the output mapping map the z1D_Action field from SYS:Message Box to a temp field in your form.
- When the dialog is opened, if yes is selected, it will set the z1D_Action = "Yes", the same happens with "No".
3) Have your workflow only fire if the returned z1D_Action value = "Yes"
I hope that helps,