Macro problem

[one_more_cave_dweller]

I have a macro that copies information from a sheet each day and pastes it horizontally into a summary sheet for the month. (a1=1st, a2=2nd etc.).
The macro is triggered by a control button in the first sheet the user clicks after they have entered the information. How can I stop them from entering the same day twice? I have tried cell validation but that only stops the first column from being repeated. I need the macro to stop if the first column (a) is a repeat.

Thanks

 

[macb]

Try the following

Use the following code in the beginning of your. It will insert today's date in cell (X1) when user clicks on your button first time. Change (X1) according to your settings.

If IsEmpty(Cells(1, 24)) Or Cells(1, 24) <> Int(Now()) Then
    Cells(1, 24) = Int(Now())
' Your code here
else
msgbox "Already copied"
End if

Regards

Mac