I would have Inventorization just send Column G as an array and have Summary do the work of parsing the array and filling in the cells.

If The Thisworkbook Code Page in Project has this code 
Public Property Let NewRecord(Input As Variant)
   'Code to parse Input (array) and do the work on the sheet
   'Can use other subs
End Property
Then all the Inventorization books have to do is connect to Project and send 
Project.xlsm.NewRecord = Array_Of_ColumnG
'exact Wording depends on Code of Project and Inventorization
BTW, "Project" is a bad name for a workbook