Create a running total, let's call it 'clear':
Fields to Summarize: {name}
Type of summary: Count
Evaluate: check 'use a formula' then ->x+2 button and enter your code:
{stock} = 0
Reset: check 'Never', if you want to summarize it for a whole report or
check 'On change of group' and select the group you would like to do this calculation for.