Advice needed to speed this code.

[offthelip]

Hi,
apologies for my incomplete answer, but try this which uses the same technique but does a double loop

Sub test()
With ThisWorkbook.Sheets("Sheet1")
    lLR = Cells(Rows.Count, "A").End(xlUp).Row
End With

inarr = Range("AY59:EX" & lLR)
 'assigning the main loading formula
Application.StatusBar = " Automated Planning : Computing ...."

 '    With Range("AY59:EX" & lLR)
 '        .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))))))"
 '        '.Application.Calculation = xlCalculationAutomatic
 '        .Value = .Value
 '    End With

endarray = 59 - lLR
' column ex is column 154 column ay is column 59
endcol = 154 - 51

For i = 1 To endarray
For j = 1 To endcol
    inarr(i, j) = "=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))))))"
Next j
Next i

Range("AY59:EX" & lLR) = inarr
End Sub