Can anyone tell me what the format of the string is that is required in order to update a Sharepoint column that is defined as a choice field with multiple selections (checkboxes are displayed when you view the properties in Sharepoint).

The format appears to be:

value1; value2; value3

When I build a string in this format, it doesn't work - none of the options are selected when I go to edit properties.

If I put a single value (eg. value1), it works, and when I edit properties, it displays the correct option checked as desired.

I have tried to build a string, assign this to a data field, and then use this to update the metadata (this is what I need to achieve eventually)

I have also tried setting the values directly by choosing them through the gui that is presented from within K2 designer (Visual Studio).
Neither method seems to work.

Has anyone actually managed to update a multiple select field on a sharepoint document library?

Thanks in advance for any assistance on this - it is driving me insane!!!