How can I clean this up?

Regex.vb

    Public Sub Regex()
        Dim strRegex As String
        strRegex = GlobalModule.RegexAccount(mSubject)
        If strRegex = "ACC# NOT FOUND" Then
            strRegex = GlobalModule.RegexCustomer(mSubject)
            If strRegex = "CUST# NOT FOUND" Then
                strRegex = GlobalModule.RegexAccount(mBody)
                If strRegex = "ACC# NOT FOUND" Then
                    strRegex = GlobalModule.RegexCustomer(mSubject)
                    If strRegex = "CUST# NOT FOUND" Then
                        strRegex = "UNKNOWN"
                        _IsValid = False
                    End If
                End If
            End If
        End If

        mCustAcc = strRegex
    End Sub