Multi-select drop down list stops working once I protect the worksheet

[kaliog7]

I am having an issue with my drop down list which are multi select. When I protect the work sheet so that certain cells cannot be altered or accessed my multi list function stops working. It will only let me select one value from the drop down box but as soon as I unprotect the worksheet it lets me select multi values from my drop down list. Please help I have googled and asked many people but no one seems to have an answer.
Thank you,
K