With C31 selected -

Data / Validation / Custom / Formula : =C45=0

Also see Input msg & Error alert tabs

Copy (or drag) C31 down to C41

Regards,
Peter T

"Cooie" wrote in message
...
Hi
I'm fairly new to this but grateful for any help. I need a warning or
message box to pop up and stop invalid data being entered.
If the user enters a value in a range (C31:U41) that causes a negative
value
in another range (C45:C55), then this is invalid data and they need to try
again with correct data.
Hopefully there's a simple answer to this.