SAP PI: ANSI X.12 Format SE01 Segment

Hi Experts,

We are using SAP PI 7.31 and I have to do a mapping for an ANSI X.12 850 document.

My question is:

In the SE Segment, data element "96" is for the number of included segments from ST to SE segments. How can I count these segments to transfer the number in this document?

Is there a way to do this with the graphical mapping tool?

Thanks.