T26P DSS keys to show used line

[hwtsai]

In my office, we have 7 phone lines from provider. And we are using Grandstream pbx server with 30 Yealink client handset. One of our client handset is T26P which has 10 DSS keys on the left side.

Now i need to configure DSS Key 1 to correspondence with line 1, DDS Key 2 with line 2 and so on, so when someone from other client handset is using line 5 for example, the light of DSS Key 5 will turn on, just like conventional pabx system. Then we will know how many lines are still available.

Could someone please give me a clue on how to do that? Thx in advance.