@dharr @Thomas Richard Sorry I misunderstood. This is what happens if I use your approach:

@Scot Gould Thank you for your reply and your willingness to make a request. I also would like to take the opportunity to thank you for your excellent website. Being in transgression from Mathcad to Maple, it helped me a lot. Especially your step-by-step approach is highly appreciated as it is something difficult to find.

@Thomas Richard thank you for your always useful replies. Below is how I as an apprentice do it momentarily:

@Thomas Richard  thank you for your reply. I was aware of the fact that you can use output=DataFrame, but this does not solve my issue, as the first row of the xlsx file will not automatically upgrade to a column header. For the moment I first have to isolate that row, convert it to a name and then use it as column header. I was wondering whether this could be done in a more easy way. The first row in Excel would consist out of of strings. Thanks again

@Thomas Richard  thank you for your prompt reply. I really appreciate your help, maple has so many possibilities, but I have to admit the learning curve is for me not always flat. :)

@mmcdara thank you so much!

@mmcdara in the previous example the statement M[1]-M[i-1] was used, but if I want to make an alternative approach M[i]-M[i-1] this gives the message "invalid subscript selector" How should I adapt the procedure in order to make this work.

The results in that case would be [-2.787,-8.341,-13.829]

I apologize for these probably simple questions but the approach is somewhat different to Mathcad which I used before. Anyway, thank you for your help.

@mmcdara thank you for your prompt reply and clear explanation. I appreciate all your help in this forum.

@Thomas Richard thank you so much for your swift reply. Your solution works fine. Have a nice weekend.

@acer thank you for this additional approach. I am always amazed about what is possible.

@Christopher2222 thank you for this suggestion. This certainly would help. When looking at Maple Flow it actually converts immediately to the lowest dimension, e.g. 'm' and 'cm' would give a result in 'cm' which you can adapt as desired. 

@mmcdara thank you for your reply and of course you are right, but I believe it would be much faster if Maple would choose a unit let us say minutes and then by just right-clicking changing the unit in the one you want. 

@Preben Alsholm thank you for your prompt reply and solution. Is this always necessary? Why does maple not do the conversion by itself?

@acer thank you so much for the clear and straightforward example. I really appreciate your time and help.

@rlopez thank you for the link, I certainly will study its contents.