2: A Subroutine to call that function for each cell in range (i12:z12) that contains content that exactly matches a sheet name in ThisWorkbook

Sub SearchRange_I12toZ12(wsToSearch_ As Worksheet)
    Dim rngToSearch As Range, rngX As Range
    Dim wsSheet As Worksheet
    Set rngToSearch = wsToSearch_.Range("I12:Z12")

    For Each rngX In rngToSearch
        Set wsSheet = ReturnWorksheet(rngX.Value)
        If Not wsSheet Is Nothing Then
            '/You now have one of many worksheets that will be operated upon, with code that sounds like simply uses...
            '/...some combination of copying content, updating, or replacing operations that should be simple to do using this structure
        End If
    Next rngX
        
    
End Sub

Function ReturnWorksheet(strWSName_ As String) As Worksheet
    Dim wsSheet As Worksheet, wsOutput As Worksheet

    For Each wsSheet In ThisWorkbook.Worksheets
        If wsSheet.Name = strWSName_ Then
            Set wsOutput = wsSheet
            Exit For
        End If
    Next wsSheet
    Set ReturnWorksheet = wsOutput
End Function