More flexible error checking while parsing CSV

Question

Right now, the input is like a list of fields:

"field1", "field2", field3", ...

And each of those fields match up with a string in the fields array based on the client's specifications.

I parse all of the fields and put them into a dictionary to use outside the function, the key being their corresponding name from the fields array. Then as a check if the input isn't way off base, I compare the length of the dictionary to the length of the fields array (+- 1 for a bit of flexibility).

Finally, the function returns True or False based on how "off" the input field length is from the fields array. The problem is the client will add additional fields like that may cause errors.

Is there a more flexible way to do this check to reduce the chance of these errors in the future?

Greatly appreciate your input.

Public Function parseCsv(ByVal csv As String, ByRef dict As Dictionary(Of String, String)) As Boolean
        
        Dim fields As String() = New String() {"Patient_Name", "Date_of_Birth", "Address", "County"}

        dict = New Dictionary(Of String, String)
        Dim csvRegex As String = "(?:,""|^"")(""""|[\w\W]*?)(?="",|""$)|(?:,(?!"")|^(?!""))([^,]*?)(?=$|,)|(\r\n|\n)"
        Dim fieldCount As Integer = 0

        Try
            Dim matches As MatchCollection = Regex.Matches(csv, csvRegex)
            Dim m As Match
            For index As Integer = 0 To matches.Count - 1
                m = matches(index)
                Dim fieldValue As String = ""

                If m.Groups(1).ToString() IsNot "" Then
                    fieldValue = m.Groups(1).ToString()
                ElseIf m.Groups(2).ToString() IsNot "" Then
                    fieldValue = m.Groups(2).ToString()
                ElseIf m.Groups(3).ToString() IsNot "" Then
                    fieldValue = m.Groups(3).ToString()
                End If
                If index < fields.Length Then
                    dict.Add(fields(index), fieldValue)
                End If
                fieldCount += 1
            Next
        Catch ex As Exception
            Return False
        End Try

        Return fieldCount = fields.Length Or fieldCount = fields.Length - 1 Or fieldCount = fields.Length + 1
End Function

Unfortunately, the input comes in as a big list of data and I can't control what it looks like.