@tomleslie @Rouben Rostamian

Thank you for your suggestions. I think the equations need to be reformulated as I found that this formulation has a singularity.

Thank you for you valuable answers and suggestions.

@Carl Love 

That is OK. The variable name is quite confusing because of the letter j, but this makes sense for me while I read and write the code.

Thank you so much.

@Carl Love 

I will give an example to simplify and make sure that I understood you correctly. Let us say that:

FyjR=10+j
m=3

then the sum results will be

((10+j)+2*(10+j)+3*(10+j)=60+6j) Not (11+12+13=36) ???

I am pressty sure that the answer is 36 and I have checked for this simple exaple and got 36.

FyjR and similar terms are functions of (t, x,y,z,thx,thy, and j) and I want to evaluate the summation by changing j from 1 to m. Do you think that I did this wrongly?

Thank you so much fro your interset. 

@Rouben Rostamian  

Thank you so much. I understand your point. I have learned this before, but it was too many years before. I will try and let you know if I have more problems. Thank you so much.

@Rouben Rostamian  

thank you for your reply. 

You mean that I need to reformulate my system into 10 first order ODEs like what we usually do in Matlab?

The second thing is, what is the calling syntax of explicit Euler methiod in Maple? 

Thank you so much.

Thank you Preben and Carl. I will try this way.

Thank you very much for your help.