Take a look at ErrorCheckingOptions in VBA's help.
From there, you can click on "see also" and go to "Error Object" and see code
like this:
Option Explicit
Sub testme01()
Dim myCell As Range
Set myCell = ActiveSheet.Range("B3")
If myCell.Errors.Item(xlNumberAsText).Value = True Then
MsgBox "Might be an error"
Else
MsgBox "nope, not even a warning"
End If
End Sub