修改VBA代码，实现以下需求， 1.F列值如果只有三个字字符串，则清空该单元格 2.将表1的B列值与表2的N列值匹配，如果匹配一致，则将表2的O列值返回给表1的E列 3.如果上一步匹配不成功，则将表1的F列的值与表2的J列值匹配，如果匹配一致，则将表2的k列值返回给表1的E列， 4.如果上面三步都匹配不成功，则将表1的D列值与表2的G列匹配，如果匹配一致，则将表2的H列值返回给表1的E列。 5.如果第一次匹配一致，后两次匹配不执行，如果第一次匹配不一致，第二次匹配一致，则第三次匹配不执行，

以下是修改后的VBA代码，注意要在正确的工作簿中运行代码：

Sub matchAndReturn()
    Dim ws1 As Worksheet, ws2 As Worksheet
    Dim lastRow1 As Long, lastRow2 As Long
    Dim i As Long, j As Long
    Dim matchFound As Boolean
    
    Set ws1 = ThisWorkbook.Worksheets("表1")
    Set ws2 = ThisWorkbook.Worksheets("表2")
    
    '清空F列只有三个字符的单元格
    lastRow1 = ws1.Cells(ws1.Rows.Count, "F").End(xlUp).Row
    For i = 2 To lastRow1
        If Len(ws1.Cells(i, "F")) = 3 Then
            ws1.Cells(i, "F").ClearContents
        End If
    Next i
    
    '匹配表1的B列和表2的N列，返回O列值到表1的E列
    lastRow1 = ws1.Cells(ws1.Rows.Count, "B").End(xlUp).Row
    lastRow2 = ws2.Cells(ws2.Rows.Count, "N").End(xlUp).Row
    For i = 2 To lastRow1
        matchFound = False
        For j = 2 To lastRow2
            If ws1.Cells(i, "B") = ws2.Cells(j, "N") Then
                ws1.Cells(i, "E") = ws2.Cells(j, "O")
                matchFound = True
                Exit For
            End If
        Next j
        If matchFound Then
            Exit For
        End If
    Next i
    
    '如果第一次匹配不成功，匹配表1的F列和表2的J列，返回K列值到表1的E列
    If Not matchFound Then
        lastRow1 = ws1.Cells(ws1.Rows.Count, "F").End(xlUp).Row
        lastRow2 = ws2.Cells(ws2.Rows.Count, "J").End(xlUp).Row
        For i = 2 To lastRow1
            matchFound = False
            For j = 2 To lastRow2
                If ws1.Cells(i, "F") = ws2.Cells(j, "J") Then
                    ws1.Cells(i, "E") = ws2.Cells(j, "K")
                    matchFound = True
                    Exit For
                End If
            Next j
            If matchFound Then
                Exit For
            End If
        Next i
    End If
    
    '如果前两次匹配都不成功，匹配表1的D列和表2的G列，返回H列值到表1的E列
    If Not matchFound Then
        lastRow1 = ws1.Cells(ws1.Rows.Count, "D").End(xlUp).Row
        lastRow2 = ws2.Cells(ws2.Rows.Count, "G").End(xlUp).Row
        For i = 2 To lastRow1
            For j = 2 To lastRow2
                If ws1.Cells(i, "D") = ws2.Cells(j, "G") Then
                    ws1.Cells(i, "E") = ws2.Cells(j, "H")
                    Exit For
                End If
            Next j
        Next i
    End If
    
    '如果第一次匹配一致，后两次匹配不执行
    '如果第一次匹配不一致，第二次匹配一致，则第三次匹配不执行
End Sub