try this 
Sub Main_Normal_Calculation()
    With Application
         '.Cursor = xlWait
        .ScreenUpdating = False
        .DisplayAlerts = False
        .EnableEvents = False
        .Calculation = xlCalculationManual
    End With
     
    startTime = Timer
    Dim lLR As Long
     
    'Call Block_date_Start_Date
     
    MsgBox "Block_date_Start_Date took " & Timer - startTime & " secs."
    startTime = Timer
    
     
    With ThisWorkbook.Sheets("Shadow_Normal_Calc")
        lLR = Cells(Rows.Count, "A").End(xlUp).Row
     
         'assigning the main loading formula
        'Application.StatusBar = " Automated Planning : Computing ...."
        Range("AY59").Formula = "=IF(OR($AF59="""",$AF59="""",$AJ59=""""),0,IF(AY$58<$AJ59,0,IF(AY$58>=$AJ59,IF(0<($AN59),MIN(($AN59-SUM(AX59:$AX59)),$AO59,SUMIF(Shadow_Dept_Lines_Sum_Col,$AM59,AY$4:AY$56)-SUMIF($AM$58:$AM58,$AM59,AY$58))))))"
        With Range("AY59:EX" & lLR)
            .FillDown
            .Calculate
            .Formula = .Value
        End With
         
         'assigning the Load control qty
        'Application.StatusBar = " Automated Planning : Computing the Load Control qties"
        Range("AW59").Formula = "=AN59-SUM(AY59:EX59)"
        With Range("AW59:AW" & lLR)
            .FillDown
            .Calculate
            .Formula = .Value
        End With
    End With
     
    MsgBox "Main Code took " & Timer - startTime & " secs."
     
     
     
    With Application
        .Cursor = xlDefault
        .ScreenUpdating = True
        .DisplayAlerts = True
        .EnableEvents = True
        .Calculation = xlCalculationAutomatic
    End With
     
End Sub