At the minute I am running this code...

Private Sub Worksheet_Change(ByVal Target As Range)
Dim rng As Range
If Not Intersect(Target, Range("e273:g284")) Is Nothing Then
Set rng = Range("e273:g284")
ElseIf Not Intersect(Target, Range("g273:j284")) Is Nothing Then
Set rng = Range("g273:j284")
ElseIf Not Intersect(Target, Range("j273:l284")) Is Nothing Then
Set rng = Range("j273:l284")
End If
Application.EnableEvents = False
If Not rng Is Nothing Then
If Application.CountIf(rng, Target.Cells(1, 1).Value) > 1 Then
MsgBox "This vehicle is booked out at this time"
Target.ClearContents
Target.Cells(1, 1).Select
End If
End If
Application.EnableEvents = True
End Sub

the code is perfect for what i need it to do but the only problem i have is that the codes roll on from each other... I.E:-

E273:G284 - G273:J284 - J273:L284

first ends in G second starts in G, Second ends on J third starts on J

for some reason this doesnt work, the first code gets the prority and works but the second works in all the columns except the first one.. in this case the first code is fine, second actually works from H not G and third works from K not J

can anyone suggest how i can overcome this problem?

Many thanks, Nick