How to grab a field from parent during import?

I would like to import records from a table into another table with a different parent. During the import the record must be linked automatically to the current parent but I don't know how!!!

I have a table BLEND linked to a table BLEND COMPONENTS (one to many). I would like to divide this BLEND in periods so I created a table BLEND PERIODS and for every blend period I would like to import all the components from a specific blend. I can import these components but during that import I can not link it to that specific blend period. Is there someone who can help me with this or is there a better way to solve this?  I found (and tried) already a lot of similar cases from this community but this was not very successfull . You're my only hope. Thanks in advance