Procedure 'usp_GetDatePeriodFromTo' expects parameter '@YEARMONTH', which was not supplied.

I am using the enterpriselib 2.0

Public Function GetBusinessCalendarPeriod(ByVal DatePeriod As String) As DataTable
           ' DatePeriod is the YearMonth
            Dim retVal As New DataTable("BusinessCalendars")

            Dim cmd As DbCommand
            Dim tmpds As DataSet

            Try
                'We get the divisions
                cmd = dbManager.GetStoredProcCommand("SENZA.dbo.usp_GetDatePeriodFromTo")

                'Temporarilly put the results in a dataset so we can check for valid data
                tmpds = dbManager.ExecuteDataSet(cmd)

                'We must ensure that only one table was returned in the execution of the query
                If tmpds.Tables.Count.Equals(1) Then

                    'We also need to ensure that there is data
                    If tmpds.Tables(0).Rows.Count > 0 Then

                        retVal = tmpds.Tables(0)

                    Else
                        Return retVal
                    End If
                Else
                    Return retVal
                End If

            Catch ex As Exception
                Throw ex
            Finally
                'Cleaning up
                If Not tmpds Is Nothing Then
                    tmpds.Dispose()
                End If

                If Not cmd Is Nothing Then
                    cmd.Dispose()
                End If

            End Try

            Return retVal
        End Function
Procedure 'usp_GetDatePeriodFromTo' expects parameter '@YEARMONTH', which was not supplied.

Private Sub cmdProceed_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles cmdProceed.Click
        _calendar.GetBusinessCalendarPeriod(txtPeriod.Text)
        Response.Write("Calendar")
    End Sub