JMCF: Update more than one custom field

[Jonny Polivka]

The short, how can I update another custom field of the same issue?

I have code that runs through a calculation and returns the result to a JMCF custom field and attempting to copy the value to another custom field using setFieldValue but run into the error.

java.lang.IllegalStateException: Calling setFieldValue() from this context is not authorized.

Does that mean the control doesn't exist yet? Any tricks to get this working?

Update:

Forgot to add that I have code that allows overwriting the calculated value so the other field's role is to always display the calculated value.

Clear as mud?

Thanks.