Need VBA to create new Workbook and name it based on cell value in original file

I had another look. I realized that what was slowing the macro down was all the formulas calculating. The following macro turns off calculation until the macro runs and now it works fairly quickly. Give it a try.

Sub SumValues()
    Application.ScreenUpdating = False
    Application.Calculation = xlCalculationManual
    Dim LastRow As Long, Val As Range, ws As Worksheet, desWS As Worksheet, srcRng As Range
    Set desWS = Sheets("Summary_Cash_Flow")
    desWS.Range("C5:PG14,D18:PG22,C26:PG31,D35:PG36,C40:PG40,C44:PG47").ClearContents
    LastRow = Cells.Find("*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row
    For Each ws In Sheets
        If ws.Name Like "Cash_Flow_*" Then
            Set srcRng = ws.Range("C5:PG14,D18:PG22,C26:PG31,D35:PG36,C40:PG40,C44:PG47")
            For Each Val In srcRng
                desWS.Range(Val.Address).Value = desWS.Range(Val.Address).Value + Val.Value
            Next Val
        End If
    Next ws
    Application.Calculation = xlCalculationAutomatic
    Application.ScreenUpdating = True
End Sub

I would have to review all the previous posts and macros that were used to try to remember what I did. It would make it easier and faster if you could attach a file with the varying start and end dates and explain in detail what the issue is.