Select the cells
Choose DataValidation
From the Allow dropdown, choose Custom
In the Formula box, type a formula that refers to the active cell, e.g.:

=OR(B5=0.75,B5<=0.25)

Click OK

Pete wrote:
How can I restrict entry to ceels between the times of
18:00 & 06:00, this must allow 22:00 etc

This is so it covers the night shift in 24hr format

Pete


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html