summations with changing variables

Hi all, i'm a student working on some code to work solve thermal stresses that occur within laminated composites. I have been able to solve the probelm given to me using brute force but I'm looking to rewrite the code so it can be used more universally applied when given different amounts of plys. The issue I'm running into when using summations is when you move from ply-to-ply becasue the thickness may change for each ply. The equation shows the components of the reduced stiffness matrix multiplied by the thermal expansion components but with its all multiply by the differnence of the plys thats where im struggling. If anyone could help me out with setting up the summation code for this it would be extremley helpful, and I hope my description of the problem makes sense. In the quation the 'h' value is the distance from the midplane.

where h,

[Matt J]

What is the input data and in what Matlab form is it held? What are the unknown variable? h_k? If so, you need more than one equation to solve for all the h_k.