No. The 5680 measures all frequencies present on the input signal. The way power meters are built, there just isn't a way to distinguish between frequencies. You could use a spec an to do this.
For example, there isn't a way to have the power meter measure the power level of a signal at 1 GHz without including the power from a (large) signal at 2 GHz. Note that smaller signals probably won't matter to you. If the signal you want to ignore is at least 20 dB lower than the signal you are interested in, then the measurement should be off by less than 0.05 dB.
