Work book with on time control to close in specified time

Hi Experts,
I have prepared a pre-interview test workbook to be completed by the new candidates recruited in my department. It has on time control to close the file in 45 minutes. It also has a voice reminder message in every 15 minutes. This workbook, in its open event creates a text file in excel addins folder to have the control of opening the workbook only for once. Definitely it can be bypassed by opening in another user profile / system. The password for the sample workbook attached here is "TEST2122".

My problem here is, some of the candidates says that they started the test but the file got stuck in 5 minutes and they were unable to continue.

Request review by the experts here and suggestions - are there any compatibility issues in the codes that I have used and is there any other alternate way to do this.

Thanks in advance!