As far as I understand you want to set a value for the CustomerId field when creating a new record. I would suggest the following:
1. Use the Kendo UI Grid edit event, which is fired when the user edits or creates a data item.
2. In order to determine whether user is editing an existing item or creating a new one you can use the mode isNew method as described in the article.
3. Use the model set method in order to set the new value for a field of the model.
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