Depending on the value, you can:
Create 2 elements.
One will use a 'Wildcard' for the index' to verify that the element is identifiable and exists (used in a timer)
You can then use Read 'Attribute' to read the index number and store it as text (e.g. [Index element number])
Second element will have a dynamic index attribute, which is then replaced by [Index element number].
Or, you can set index as dynamic value, for example if it only changes between 0 and 10, you can then recover when ever BP fails to identify the element and add one to the index value until it either hits the element in question or raises exception.