Blinking DataGridViewRow ErrorText

Hello all,

I have a DataGridViewCellValidating function that sets the error text based on a particular cell's input.  It calls a function called "HighlightErrantCell" which ensures the user cannot leave the problem cell without fixing it.

A MessageBox seems abrupt, but I would like some kind of animation so the user doesn't think my application is frozen when they try to click another cell.  I put a loop at the end of my HighlightErrorCell, but it doesn't do anything I notice.

Here's what I have so far:

private void HighlightErrantCell(int RowIndex)
{

            string err = grdUsers.Rows[RowIndex].ErrorText;

            //Focus on the proper cell based on the error text.
.
.
.

            //Animate the ErrorText flashing
            for (int i = 1; i <= 3; i++)
            {
                System.Diagnostics.Debug.WriteLine("Clearing Error text.");
                grdUsers.Rows[RowIndex].ErrorText = null;
                grdUsers.UpdateRowErrorText(RowIndex);
                grdUsers.InvalidateRow(RowIndex);
                System.Threading.Thread.Sleep(300);
                System.Diagnostics.Debug.WriteLine("Setting Error text.");
                grdUsers.Rows[RowIndex].ErrorText = err;
                grdUsers.UpdateRowErrorText(RowIndex);
                grdUsers.InvalidateRow(RowIndex);
                System.Threading.Thread.Sleep(300);
            }
}