crystal reports sum() with no grouping

Hi

I am producing a report in crystal reports for VS 2010

The report is listing a number of items, each categorised but not grouped.

I have 3 categories to make a sum of the units in each... so I have tried something like this

example:

nuts 3
bolts 10
nuts 3
washers 8
nuts 4
bolts 5
washers 3

Totals:
nuts: 10
bolts: 15
washers: 11

Local NumberVar tot;
if {Command.group} = 0 Then
    tot := tot + {Command.units};

tot

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but this isn't working as expected... how can I achieve the results I need?