>How do I validate the data entered into a textbox in a cell against the value of a boundcolumn of the same row? I want to make sure the value entered in the textbox is evenly divisible by the value in the boundcolumn.

You can use the Validating event for the cell (or column) that you are editing in. The binding manager should know which row you are in in the dataset (or rather the datatable in the dataset or just the datatable). Then do your math and if the math doesn't make you happy you execute e.Cancel = true and focus goes back to that cell.

Hope that helps

Einar