How to directly get First Derivative band images from hyperspectral reflectance band images (0 to 288 bands) using ENVI software or band math??

1. I have the stacked reflectance 288 bands in a .dat file.

2. I want to know how to convert reflectance spectral bands to first derivative reflectance spectral bands by using mathmatical matrix to obtain spectral derivative value in ENVI.

If you can provide band math equations or IDL code, it would be really greatful.

Thanks in advance and cheers.