You are making the same mistake twice...
The initial value in your inner nested while loops
need to be set every time the inner loop executes.
Like this:
#local A = from#;
#while (A <= to#)
#local B = from#;
#while (B <= to#)
... process
#local B = B + step#;
#end
#local A = A + step#;
#end
