crystal reports – need to subtract variables in subreports

Hi, I have a crystal report (IX) called BPCTaskReportV3. I have a subreport called totalworkflowsum, with formula called @wfssubmitted, which contains:

WhilePrintingRecords;
Shared NumberVar totalwfs;

totalwfs := DistinctCount ({Reviewers_ALL_Table_BE.WorkflowID})

Another subreport is called NoReviewWorkflows, with a formula called @noreview, which contains:

WhilePrintingRecords;
Shared NumberVar noreviewwfs;

noreviewwfs := DistinctCount ({Reviewers_ALL_Table_BE.WorkflowID})

I need to subtract the total of @noreview from @wfssubmitted. In order to do this, I’ve created a formula called @mytotal, which contains:

WhilePrintingRecords;
Shared NumberVar mytotal;
mytotal={BPCTaskReportV3.totalworkflowssum.totalwfs}-{BPCTaskReportV3.NoReviewWorkflows.noreviewwfs}

I’m getting the error message ‘this field name is not known’ for BPCTaskReportV3.totalworkflowssum.totalwfs. I’ve tried other variations of this, such as BPCTaskReportV3.totalwfs and totalworkflowssum.totalwfs and BPCTaskReportV3.totalwfs. Is there another syntax I shoulde be using?