how to add a character into cells in a row of a datagrid?

Hi, i've been looking around yesterday in the web and i came to here... here's my problem: i have this datagrid, and i want to add a % character into the 7th and 8th rows, after the first column... i've been looking into several forums, and all i find is columns, columns and more columns.... but rows? mmmnot much... greetings from chile!

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