first of all you need to find out the method to store the waveform displayed by your CRO on PC then you will get this as *.txt tile or some kind of file.....I think LeCroy support that....then you need to read the Values of this from PC as and array apply FFT to it to get the require analysis like DC component....frequency component contribution from the magnitude spectrum.....or some statical method like average value of array and range of variation as maximum value of array - Minimum Value of array the you can get the percentage variation as 100*(range/average value).....if you have more than 10 significant contribution from different frequency component then you need bit complicated analysis method....
Good Luck