For Loop for an m-by-1 matrix

Hello guys, I can not figure out how to make a for loop for a m-by-1 matrix (hence a 1 column vector) with which I start at the second element and subtract the previous element and then repeat this operation on the following elements.

How can I do this ?

for example I have an excel column called "Ref" that is made by these numbers:

Ref

839825

851892

851955

851969

851964

851518

851953

850544

I need something that in matlab will do for me :

851892-839825 =

851955-851892 =

ecc...

and create another column called :

Ref(j) - Ref(j-1)wih under it all the calcutated subtractions

Any help please ?

Thnak you