Don't really know what i am doing with this but this is what i have got so far do you think it will work?
I want it to find an overdue vessel from the ETR field 30min after the time stated in the ETR field.
Install On Timer Script ["OVERDUE_VESSEL"; Interval: 1800]
Enter Find Mode 
Set Field [NEW RADIO LOG::ETR; "<" & Get(CurrentTime) + 300]
Set Error Capture [On]
Perform Find 
And do you get this script to run in the File Options just under switch to layout by ticking that box?