Changing a value using a look-up table

Dim temp As Variant

    temp = "dummy value dude"
    
    On Error Resume Next
    temp = WorksheetFunction.VLookup(Range("G2"), Sheets("Sheet2").Range("A:B"), 2, False)
    On Error GoTo 0
    
    If temp <> "dummy value dude" Then
    
        Range("G2") = temp
    End If</code


Having said that, I think what you need to do is have another column for temp basis. Let say its column H on sheet 1

Do a lookup there

as 

<code>    Range("G2").Select
    
    'doing a look up in temp range H
    With Range("H2:H" & sPostDelLastRow)
        
        'actual look up. If look up fails, then use corresponding value from G column else use the value of vlookup
        .FormulaR1C1 = "=ISERROR(VLOOKUP(TRIM(RC[-1]),WCSSCustItemNumLookupTable!R1C1:R2000C2,2,0)), RC[-1], VLOOKUP(TRIM(RC[-1]),WCSSCustItemNumLookupTable!R1C1:R2000C2,2,0)"
        
        .Copy 'copying
        
        .PasteSpecial xlPasteValues 'pasting back as values to eliminate the formula
        
        .Copy 'copying again to move to actual G range
    
    End With
    
    'copy to G range
    Range("G2:G" & sPostDelLastRow).PasteSpecial
    
    'clear teamp range
    Range("H2:H" & sPostDelLastRow).Clear