Total incorrect when trying to summarize using a variable

Question

I have a report with two subreports that summarize labor cost and material cost.  I need to return the material cost total to the main report so I created a shared variable.  The correct value is returned each time I display this variable in the main report.  Now I need to display a group total of the material cost and summarize the formula field that uses this variable.  The formula for displaying the variable with the value set in the subreport is {@MatSubTotal}:
Shared NumberVar myTotal;
myTotal;
This field on my report is correct.  I created a second variable call SumTotal which I set to 0 in my group header.  Then after the formula field listed above, I added a new formula: (I left it in the details section until I knew it was working correctly and then I plan to just display the total in the group footer)
WhilePrintingRecords;
Shared NumberVar SumTotal;
SumTotal := SumTotal + {@MatSubTotal};
Here is where I run into problems.  The first time my subreport displays, the group total is correct, but then the material subreport is supressed and {@MatSubTotal} is 0, but my group total adds the previous value so now the amount is double what it should be.  From here on out, the group total is calculated correctly even when the material subreport is supressed and returns 0.  Just that one time the SumTotal adds the previous value when it should be adding 0 and the whole total is off.  Any suggestions?  Also, my report has three groupings so do I need three separate variables to track the material total for the group?  Just trying to figure out the best way to summarize the variable I'm returning from the subreport.  Thanks

Answer 1

Thank you everyone for the help.  I thought I'd found it with this last suggestion--there is a condition on the details section that I wasn't aware of:
not({workorder.actmatcost}+{workorder.actlabcost}>0)
However, I copied the same condition to my formula, but I still get the same result.
iif(({workorder.actmatcost}+{workorder.actlabcost}>0),SumTotal := SumTotal +1,SumTotal); 
It definitely seems like the formula is being incremented when I can't see it on the report, but the only conditions I can find all have to do with the material cost being zero anyway so it shouldn't matter if that was added to my total.  I just can't figure out how the previous value is added more than once.  I swear once I figure out what the cause is, it will seem like such a simple fix, but I've tried so many things so far with no luck!?!
There's also a condition to suppress the material subreport (within the Details section)
isnull ({matusetrans.wonum})
but I can't try that on the main report since it doesn't use that table.  And that condition is equal to the one above anyway in terms of the data from the two different tables.  Maybe at this point I should just try rewriting the report since I'm not familiar with exactly how it was created in the first place.