You can use the row index you find with GetRowWithCellText("LABEL1") with ChildObjects() of the WebTable to check your class property. Something like:
Code:
Set desc = Description.Create
desc("micclass").Value = "WebElement"
desc("html tag").Value = "TR"
row = Browser("Browser").Page("Page").WebTable("LABEL1").GetRowWithCellText("LABEL1")
Set rows = Browser("Browser").Page("Page").WebTable("LABEL1").ChildObjects(desc)
rows.Item(row-1).CheckProperty "class", "xxx yySelected"