Excelで、元データ(CSV)から読み込んできて

質問に書かれた仕様と少し変えてしまいましたが、下記のようにしてどうでしょうか。

csvFilePath の行に読み込む CSV ファイルのパスを書いて実行下さい。
不明な点があれば、コメント下さい。

Option Explicit

Const csvFilePath = "D:\Data\Reserve.csv"  '// 読み込む CSVファイル名

'-----------------------------------------------------------------------------------
Sub 予約表作成()
'-----------------------------------------------------------------------------------
    Dim fso
    Set fso = CreateObject("Scripting.FileSystemObject")
    
    Dim lines
    lines = Split(fso.OpenTextFile(csvFilePath).ReadAll(), vbNewLine)
    
    Dim line
    Dim inf
    For Each line In lines
        inf = Split(line, ",")
        If UBound(inf) = 4 And InStr(line, "開始日") = 0 Then setDateInfo inf
    Next
End Sub

'-----------------------------------------------------------------------------------
Sub setDateInfo(inf)
'-----------------------------------------------------------------------------------
    Dim stDate
    Dim edDate
    stDate = CDate(inf(0))
    edDate = CDate(inf(2))
    
    Dim stTime
    Dim edTime
    stTime = CDate(inf(1))
    edTime = CDate(inf(3))
    
    Dim roomName
    roomName = inf(4)
    
    If edDate - stDate > 30 Then
        MsgBox "予約期間が1ヶ月を超えています｡"
        Exit Sub
    End If
    
    Dim dt As Long
    Dim d
    If stDate = edDate Then
        SetOneDay stDate, stTime, edTime, roomName
    Else
        SetOneDay stDate, stTime, TimeSerial(21, 0, 0), roomName
        For d = stDate + 1 To edDate - 1
            SetOneDay d, TimeSerial(10, 0, 0), TimeSerial(21, 0, 0), roomName
        Next
        SetOneDay edDate, TimeSerial(10, 0, 0), edTime, roomName
    End If
End Sub

'-----------------------------------------------------------------------------------
Sub SetOneDay(dt, st, et, rm)
'-----------------------------------------------------------------------------------
    Dim wsName
    wsName = rm & Application.Text(dt, "(YYYYMM)")
    
    Dim dstWS As Worksheet
    On Error Resume Next
    Set dstWS = Worksheets(wsName)
    On Error GoTo 0

    Dim r As Long
    Dim c As Long
    Dim ed As Long
'// シート設定：なければ作成
    If dstWS Is Nothing Then
        Worksheets.Add after:=Worksheets(Worksheets.Count)
        Set dstWS = Worksheets(Worksheets.Count)

'// シートの設定
        dstWS.Name = wsName
        dstWS.Columns("B:L").ColumnWidth = 6
        ed = Day(DateSerial(Year(dt), Month(dt) + 1, 0))
        For c = 2 To 12
            dstWS.Cells(1, c).Value = TimeSerial(c + 8, 0, 0)
        Next
        For r = 1 To ed
            dstWS.Cells(r + 1, "A").Value = DateSerial(Year(dt), Month(dt), r)
            Select Case Weekday(dstWS.Cells(r + 1, "A").Value)
                Case vbSaturday: dstWS.Cells(r + 1, "A").Resize(1, 12).Interior.ColorIndex = 37
                Case vbSunday:   dstWS.Cells(r + 1, "A").Resize(1, 12).Interior.ColorIndex = 38
            End Select
        Next
        dstWS.Range("A2").Resize(ed, 1).NumberFormat = "mm月dd日"
        dstWS.Range("B1").Resize(ed + 1, 11).NumberFormat = "h:mm"
        dstWS.Range("A1").Resize(ed + 1, 12).HorizontalAlignment = xlCenter
        dstWS.Range("A1").Resize(ed + 1, 12).Borders.Weight = xlThin
    End If
    
'// 時間の記入
    Dim t
    Dim h As Long
    With dstWS
        For h = Hour(st) To Hour(et)
            t = WorksheetFunction.Min(et, TimeSerial(h + 1, 0, 0)) - WorksheetFunction.Max(st, TimeSerial(h, 0, 0))
            If t > 0 Then .Cells(Day(dt) + 1, h - 8).Value = .Cells(Day(dt) + 1, h - 8).Value + t
        Next
    End With
End Sub