Setting correct scope for a Report Builder 3.0 indicator

I have a report with a top level group containing columns Software title, Licenses and Installed copies and in a child group I have the computer names

I have created an indicator with an expression to set the state.  

=Switch(Fields!Licenses.Value>Fields!Installed_copies.Value,75, Fields!Licenses.Value=Fields!Installed_copies.Value, 50,Fields!Licenses.Value<Fields!Installed_copies.Value,25)

The > and = evaluate ok but the < does not.  I can only imagine that in the child group each computer has one installed copy which evaluates as 50 for one actual license.

I need to evaluate the indicator at the top level parent group (e.g. 1 license < 4 installed copies evaluates as 25)

Thanks

David