How to determine if Microsoft Excel is not installed?

Dim path As String
        path = AppDomain.CurrentDomain.BaseDirectory
        'MessageBox.Show(path)
        'Export DataGridView to Excel
        Dim xlapp As Excel.Application

        Dim xlworkbook As Excel.Workbook
        Dim xlworksheetAmort As Excel.Worksheet
        Dim xlworksheetSOA As Excel.Worksheet
        Dim misvalue As Object = System.Reflection.Missing.Value
        Dim i As Integer
        Dim j As Integer

        xlapp = New Excel.Application
        xlworkbook = xlapp.Workbooks.Open(AppDomain.CurrentDomain.BaseDirectory + "Template.xls")
        xlworksheetAmort = xlworkbook.Sheets("Amort")

        xlworksheetAmort.Cells(1, 1) = "Period"
        xlworksheetAmort.Cells(1, 2) = "Principal"
        xlworksheetAmort.Cells(1, 3) = "Interest"
        xlworksheetAmort.Cells(1, 4) = "Payment"
        xlworksheetAmort.Cells(1, 5) = "O/S Balance"

        For i = 0 To grdvwAmortization.RowCount - 2
            For j = 0 To grdvwAmortization.ColumnCount - 1
                xlworksheetAmort.Cells(i + 1, j + 1) = _
                    grdvwAmortization(j, i).Value.ToString()
            Next
        Next

        xlworksheetSOA = xlworkbook.Sheets("SOA")

        'Account Details
        xlworksheetSOA.Cells(4, 14) = Date.Now.ToString("MM/dd/yyyy")
        xlworksheetSOA.Cells(6, 4) = lblLastName.Text + ", " + lblFirstName.Text
        xlworksheetSOA.Cells(7, 4) = getLoanType(lblLoanType.Text)
        xlworksheetSOA.Cells(12, 4).NumberFormat = "@"
        xlworksheetSOA.Cells(12, 4) = txtbxPNNum.Text

        'Copy datagridview to excel
        Dim Row As Integer = 13

        For i = 0 To grdvwSOA.RowCount - 2
            For j = 0 To grdvwSOA.ColumnCount - 1
                xlworksheetSOA.Cells(Row, j + 1) = grdvwSOA(j, i).Value.ToString()
            Next
            Row = Row + 1
        Next

        Dim dialog As New SaveFileDialog
        Dim result As DialogResult = dialog.ShowDialog

        Try
            xlworkbook.SaveAs(dialog.FileName)
            'xlworksheet.SaveAs(dialog.FileName)
        Catch exerr As Exception
        End Try

        xlworkbook.Close()
        xlapp.Quit()

        releaseObject(xlapp)
        releaseObject(xlworkbook)
        'releaseObject(xlworksheetAmort)
        'releaseObject(xlworksheetSOA)