got it!
this does what i need
for ($i = 0; $i -lt $dataInstUpdates.RowCount; $i++)
{
if ($dataInstUpdates.Rows[$i].Cells[0].value -notlike "KB$($textboxFilterUpdate.text)*")
{ $dataInstUpdates.Rows[$i].Visible = $false }
else
{ $dataInstUpdates.Rows[$i].Visible = $true }
}
thanks!