Field to count number of subforms (patients)

Hi,

New to Designer and making some headway...

I've got a field to count the number of patients on a form. Each patient's details are in a subform, which is within a container. There's buttons to add or delete a patient/subform which is working fine.

I'm struggling with getting the field to show the number of patients/subforms.

I've put this code into the 'calculate' event of the field:

$.rawValue=Count(PatientContainer.PatientDetailsSubform.Line1[*])

'Line1' is an element withing the PatientDetailsSubform. I did have it as 'Surname' but the count only goes up when it's non-null and even then it only seems to count the first subform. To be honest, Line1 doesn't work at all...

Thanks in advance,

Simon.