One way:

Public Sub Test
If Range("A1").Value < 0 Then
MsgBox "Cell A1 must be equal to zero"
Else
'your code here
End If
End Sub

Or, slightly more robust


Public Sub Test
Dim bSuccess As Boolean
With Range("A1")
If IsNumeric(.Value) Then
If .Value = 0 Then
'your code here
bSuccess = True
End If
End If
End With
If Not bSuccess Then _
MsgBox "Cell A1 must be equal to zero"
End Sub

In article ,
"Neil Jimack" <Neil wrote:

I have a macro assigned to a button, but it can only run if a particular cell
is zero. If the cell is greater than or less than zero, I want a message box
to appear telling the user that the cell in question isn't zero.

I know the code for making the Msgbox appear, but don't know the syntax for
only having the box appear if the cell in question isn't zero.

Any advice?