Using An Expression To Group On Multiple Fields

I have an exisitng report that lists unit name, provider, runday, shift, patient. The report groups by unit name and there is a page break after each unit name. So in the current environment the report prints one page per unit that contains all of the providers, rundays, shifts, and patients for that unit name its grouping on. So the report would like like this when it prints:

Unit A
Provider 1 Runday 1 Shift 1





patient 1
patient 2
Provider 1 Runday 1 Shift 2





patient 1
patient 2
Provider 1 Runday 2 Shift 1





patient 1
patient 2
Provider 1 Runday 2 Shift 2





patient 1
patient 2
Provider 2 Runday 1 Shift 1





patient 1
patient 2
Provider 2 Runday 1 Shift 2





patient 1
patient 2
Provider 2 Runday 2 Shift 1





patient 1
patient 2
Provider 2 Runday 2 Shift 2





patient 1
patient 2
PAGE BREAK
Unit B............(repeat data from page 1)
PAGE BREAK
Unit C............(repeat data from page 1

The end user would like the ability to keep the report as is but would like to also be able to print the report as one page per each unit name, provider, runday and shift. so it would look like this

Unit A
Provider 1 Runday 1 Shift 1





patient 1
patient 2
PAGE BREAK
Unit A
Provider 1 Runday 1 Shift 2





patient 1
patient 2
PAGE BREAK
Unit A
Provider 1 Runday 2 Shift 1





patient 1
patient 2




So I created a boolean parameter with a prompt of Page break by Unit, Provider, Runday & Shift? My thought is if the users sets this to False, the report will group on just Unit Name (the first example). If the user sets this to True, the report will group on Unit Name, Provider, Runday & Shift.

I set the grouping expression for this data table as:
=iif(Parameters!Grouping.Value = "False", Fields!unit_Name.Value,(Fields!unit_Name.Value,Fields!Lname.Value,Fields!Rundays.ValueFields!Shift.Value))


Within the expression editor window it displays a syntax error and the report will not run.

Any help would be greatly appreciated!!!!!!!!!