Fill Series of Disjointed Selection across Rows & Columns?

How can I quickly finish numbering the white boxes in this spread sheet?

http://i34.tinypic.com/33y6pgm.jpg

Thank you very much.

Sorry, I just need to number the empty boxes 1, 2, 3, 4 ... across the rows and start the next row with 5, 6, 7 ... This is shown in the picture in the first post.

Unfortunately, there are blank spaces in between so I can not use the Fill Series option of clicking and dragging the black cross.

The sheet represents a group of parts that are ordered in that fashion on a circular platform, the blue spaces are bad parts.

I'm looking for an easy way to number the good parts, as described above.
It seems that I should be able to select the cells of the good parts and quickly number them using a function of sorts, perhaps?

Any help would be greatly appreciated.

That doesn't seem to work, each new selection starts at 1.

Perhaps I'm selecting them wrong? (Holding Ctrl, then clicking and dragging across each row.) I'm not sure how to go about fixing the code, eek.

Thank you.