检查单元格是否为空白，如果是，填充它，然后将结果与旧值进行比较，如果不同，使用 VBA 突出显示？

Question

Im trying to have this function loop through a range of values in column Z from rows 6 to the number stored in the OS_PLs variable. I want it to check to see if there is already an invoice number in the cell...and if there is, to move on to the next cell....however if there is not, to put this match formula in to see if it can find a corresponding invoice number on the ARbalance sheet. Then, if it placed something other than the original value in the cell, to highlight the cell in orange with black hash marks.

To accomplish this I have tried to first store the initial value in a variable "valuestore"

Next I tried to make sure to clear any cells that only contain "" from the last time I ran this function (later in the macro it copys the range and pastes as values to get rid of the formulas) so that the "isempty" check will work properly.

Next I have it check if the cell is empty and if it is not, it should just move on to the next i but if it is empty, then it should input the match formula

Finally, assuming the cell was empty in the last step, it should compare the new value to the old value and if it is different, then it should highlight the cell.

For whatever reason this seems to be clearing each cell, it seems to always show nothing as the value of the valuestore variable, and it is inputting the formula in every cell. the only thing it seems to do (kind of) correctly is to highlight the cells which end up with values at the end and not highlight the cells which remain "". However, it is also highlighting the cells which originally contained invoice numbers that it has deleted and since overwritten.

Anyone have any ideas?

Thanks

For i = 6 To OS_PLs

   Dim valuestore As String
   Range("Z" & i).Value = valuestore
   MsgBox (valuestore)

    If Range("Z" & i).Value = """" Then
        Range("Z" & i).Clear
    End If

    If IsEmpty(Range("Z" & i)) Then
        Range("Z" & i).Select
            ActiveCell.FormulaR1C1 = _
                "=IFERROR(IF(LEFT(INDEX('AR balance.xlsx'!AR_Invoice_Nums,MATCH(RC[-20],'AR balance.xlsx'!AR_PL_Nums,0)),5)=""CMSHK"","""",INDEX('AR balance.xlsx'!AR_Invoice_Nums,MATCH(RC[-20],'AR balance.xlsx'!AR_PL_Nums,0))),"""")"

        If Not (Range("Z" & i)) = """" Then
            If Not (Range("Z" & i)) = valuestore Then
                With Selection.Interior
                .Pattern = xlUp
                .PatternColorIndex = xlAutomatic
                .Color = 49407
                .TintAndShade = 0
                .PatternTintAndShade = 0
                End With
            End If
        End If
    Else
    End If
Next i

Answer 1

For a blank cell Range("Z" & i).Value = """" will always return FALSE

Range("Z" & i).Value = "" will return TRUE

Range("Z" & i).Value = vbNullString is possibly a more specific test.