First to all, thank you for your good ideas.

It must be possible to send the data from slave 2 to slave 1 by using port p3.0 and p3.1
(receiving and transmitting).
Then send data from slave 1 (includes slave 1 data and slave 2 data) to master by the same way.
After that from master to pc by using simple UART. That will be all.

So my problem is to write a program in c to free port p3.0 and p3.1 for one sending slave and another receiving slave.
Like that:

For Slave 2:
if (p3.1 = 1) {send data}

For Slave 1:
if (p3.0 = 1) {receive data}


Thanks and cheers
Walter