It is possible to monitor the START/STOP status of the DL716 using communication commands. To do this, you will have to send the ":STATus:CONDition?" (without quotations) command to the instrument, in order to query the status of the Condition Register. The instrument will return a decimal number and Bit-0 will display either 1(Start) or 0 (Stop). Since the return value is a decimal number, you cannot perform bit masking.
As an example, if the DL716 is in START and measurement parameter function is ON, Bit-8 and Bit-0 will display "1." The decimal value for Bit-8 is 128 and for Bit-1 is 1, so the return value of the ":STATus:CONDition?" command is 129.
You cannot use the Extended Event Register to monitor the START/STOP status. The reason for this is because the Extended Event Register is a latch register, and you cannot monitor bit changes at the end of data acquisition from a latch register.