This macro will highlight cells in column G based on the selection in column A

HighlightCorrespondingCells.vb

Option Explicit
Private Sub Worksheet_SelectionChange(ByVal Target As Range)

    Dim wksLookups As Worksheet
    Dim lngFirstRow As Long, lngLastRow As Long
    
    'Get the Worksheet so we can confidently identify
    'the Range that we'll be highlighting (if need be)
    Set wksLookups = Target.Parent
    
    'Clear the background color in column G (7)
    wksLookups.Columns(7).Interior.ColorIndex = xlNone
    
    'First, we need to check that the selection
    'occurred in column A (1) AND was in a row after
    'row 1
    If Target.Column = 1 And Target.Row > 1 Then
        
        'Find the first and last rows of the selected
        'range in column A
        lngFirstRow = Target.Row
        lngLastRow = Target.Rows.Count + (Target.Row - 1)
        
        'Highlight the corresponding cell(s) in column G (7)
        With wksLookups
            .Range(.Cells(lngFirstRow, 7), _
                   .Cells(lngLastRow, 7)).Interior.Color = RGB(255, 255, 0)
        End With
        
    End If
    
End Sub