change cell icon/colour if empty

[Raggy]

I want to have a grid where I enter values 1 to 30 for example and in the cells that have no data in then (i.e. the person is on holiday) that it will indicate as such, tried conditions but can only seem to get them to do it if its greater than 0!
I also want to have other cells change their status i.e. show an icon or change fill colour dependant on what the first set of cells have changed to

 

[etaf]

conditional formatting should give you this info

Setup a formula using
Cell = ""

So if you select D4 to I21 as shown on the image
then
D4=""
and choose a fill colour

I also want to have other cells change their status i.e. show an icon or change fill colour dependant on what the first set of cells have changed to

Not sure what this means
BUT if it was dependant on what was in column C
then
you can fix the column using a $
so select D4:I21
and then
=$C4 = "fred"
Select a fill colour

now if fred is entered into any C column then that row from column D to I will change colour