Storing Multiple large matrixs on a loop

Good Afternoon,

I have another probably quite basic query as usual.

I am generating a series of matrix's on a loop, 501x501 double.

I am trying to save each matrix the way I normally do but I always get this response:

Subscript indices must either be real positive integers or logicals.

Error in MMM (line 81) RESULTSPACE(Sources,:) = RESULTS

Where RESULTSPACE is my storage space, Sources are the terms I'm looping through and RESULTS is my matrix.

Any pointers would be greatly appreciated!

Thank you!