Grouping and ungrouping in protected workbook

Hello All: Using Excel 2013 I have a workbook of several pages that I am protecting to eliminate any alterations to structure and limit access to locked cells. I have one page of workbook that I need to allow for users to expand and collapse rows of data that I have grouped.
I need a way of allowing for users to expand and collapse these rows by simply selecting the +/- keys on left once I've protected workbook. What I also need is to keep the structure and locked cells from being changed or accessed once the rows are expanded or collapsed.
If I need to accomplish this through VBA, please go slowly as my experience is minimal at best.

The whole intention is to allow some users the ability to have additional rows to enter data, yet for those that don't need the additional data entry, minimize the size of the document. If there is a better way to accomplish this rather than through " group - ungroup" please share with me.

Thank you all for your help.

ChemistB: Thank you for your response. I have since decided to expand rows using checkboxes instead of using +/- tabs. May have to resubmit question to reflect new approach .

Thanks again.