Why do I get the "Subscripted assignment dimension mismatch" error message?

Dear all:

I am allocating a sub-matrix to the original matrix. This time, The Matlab give above error massage, while I did many times this task but I was not facing with this error.

My problem is, as for example: I have a matrix of (101,101), and want to calculate the values for i=2:100, and j=2:100; ( i=j=101) then allocate the calculated values to the original matrix. in this Time I Face with above error massage, while in previous time , I was not facing with such error and many times I calculated the values for i=2:100, and j=2:100 in a matrix of (101,101). I wish you help me for solving this error.

Thanks in advance.

[Mischa Kim]

Can you attach your code?