Slow Writing To Large Number Of Cells

I heard there is an efficient way of writing large amounts of data at once to a worksheet. My program is writing alot of data (e.g. 600+ items in each row) and takes over an hour to run because it writes to each cell one-at-a-time. I seached this forum and couldn't find the answer. Here is an excerpt from an old 1998 article by Dermot Balson and William Mercer that used code to write to cells in large chunks but it doesn't work for me - I get a method failed message.

'to read in
Dim A As Variant 'MUST be variant, no brackets
A = Range("SomeRange").Resize(10,20) 'reads 10x20 array starting at range SomeRange
'(NB I've used Resize above but you can specify a range of cells any way you want)

'to write back to sheet
Range("SomeRange").Resize(10,20) = A
'A can be any data type but MUST be two dimensional even if you are only writing one
'column or row - first dimension is used for rows, and the second for columns
'this can be slow - see third question below for workaround..

Here is the link to the article: http://www.avdf.com/apr98/art_ot003.html. A more detailed explanation how this trick works