Dynamic global properties

I hope I understand your problem correctly and you want to essentially have a global property that changes each time you use it?

Using a timestamp for example, this is what I have for a property 'epoch'

${=Calendar c = Calendar.getInstance(); c.add(Calendar.DATE,0); c.getTimeInMillis()}

When I use ${#Project#epoch} as input in a call, each time I invoke that call it will have a new value.

Here is another example (not a property but set on the input for a particular api call) where I use a timestamp in a call with an additional identifier (the test name with spaces removed)

${=import java.text.SimpleDateFormat ;  "MYPREFEX-" + context.getTestCase().getLabel().replaceAll("\\s+","") + "-" + new SimpleDateFormat("YYYYMMdd-HHmmssSSS").format(new Date()) }

Hopefully that is helpful to you.