Spike,

What you want to do is not possible without using VBA to unmerge and
remerge cells every day, since it is not the logical set of cells
starting with Saturday that would merged but, as in your current case,
the physical sets of cells x6 through x12, x13 through x17, etc. You
will not get a lot of support for merged cells on these forums, since
the gurus tend to dislike them, generally with good reason.

Why not just turn off your grid lines and it will look as if you have
merged cells. If you then need to center text vertically in those
areas you may be able to do so through appropriate functions.

Why are you trying to merge the cells for each week? If we knew,
someone might have an alternative solution.

HTH

Declan O'R