Datagrid w/ combobox – what to pass?

I currently have a PS Form that has a datagrid on it with 4 columns created through the designer:

text | combobox | text | text 

Now when I try to add a new row via $datagrid.Rows.Add(string, ???, string, string) it blows up and says the combobox value is not valid.

I’ve tried passing in an arrayList, object and tried passing a comboboxcell (after adding items to it) but still get hit with the same error.

I have successfully added datarows with just text fields, then afterwards inserted a new column to the data table – but it makes the code a bit longer.

What is the combobox column expecting?