Find & Edit a row in a datatable

I am trying to find and edit a row in a datatable.

I set up a new datarow dr.

dr = catalogues.CatalogueTypes.Rows.Find(oldCatalogueIDCode)

Great this gets me the datarow to edit, then i

dr.BeginEdit()
dr(catalogues.CatalogueTypes.CatalogueIDColumn.ColumnName) = newCatalogueIDCode

This gives the new datarow dr a new catalogueid in the catalogueidcolumn

I then try and accept the changes

dr.AcceptChanges()
catalogues.CatalogueTypes.AcceptChanges()

BUT the dataset doesn't get updated or changed just the datarow dr.
If i specify directly the datarow eg.

dr = catalogues.CatalogueTypes.Rows(2)

This works no problems.

So, how do i find a row given a value and then edit it in the datatable and acceptchanges.

Thank you for any help.

Zac