How to solve an equation contains 2 variable range - Part Two

Dear Expert,

I'm stuck in preparing my calc sheet in determining local buckling check with few variables which are:

1) x - is the variable range for external pressure

2) i - is the variable range for bending moment.

my problem are:

1) when look at the variable range for bending moment (M), why there is still Mo=0 as i already specify i is for range 1,2 till n. This will led to an equation divide by zero

2) I'm not sure LBCin programme is correct, my aim is to check for example at External Pressure = 0MPa what is the LBCin value when bending moment (M) is from 20Nm,30Nm and so on. Then External pressure increase =0.1MPa with bending moment (M) is from 20Nm,30Nm and so on. And further on

Appreciate your assistant on the matters.

Thank you

Regards

-Akmal-