I do not believe it is possible to import data into repeating fields unless you are importing using the .fp7/.fmp12 data formats.
That being said, it's not impossible to do what you need. What you'll need to do it import the data to a temporary holding field (plain text field).
Then you can run a script after that to write the repeating values in. IE:
Replace Field Contents - table::repeatingField - repetition 1 = GetValue (table::tempField ; 1)
Replace Field Contents - table::repeatingField - repetition 2 = GetValue (table::tempField ; 2)
Replace Field Contents - table::repeatingField - repetition 3 = GetValue (table::tempField ; 3)
You might have to do some additions to the above GetValue() calculation depending on how your source data is stored (IE line numbers removed, trim spaces and such), but this would be the basic way to process repeating field values from a flat text field value.
The separater for repeating fields is ascii29... if I remember correctly. The easiest way to check is to export from a repeating field.
If the values are entered into a single cell in Excel with line breaks... then you can import the records directly then run a script that moves the values one at at ime to the other repetitions as more that likely they ended up in the first repetition. I would try copying the ascii29 separator then paste it into the excel cell between values.....
You may have to resort to text as CSV might also cause other problems.