use a double ampersands && in between the commands
so;

Net stop "dns client" && Net start "dns client"

more examples;
FORMAT A: /Q && COPY C:\DATA\*.* A:
will copy all files from C:\DATA to diskette IF and ONLY IF the format succeeds.

XCOPY C:\*.* D:\ /S 2>&1> NUL ¦¦ ECHO Something terrible happened
will display your own custom error message if XCOPY fails

the double pipes || is used to Execute command2 only if execution of command1 has finished unsuccessfully

Source

or even perhaps the Start /wait switch (which can be used with TIME)