See if this helps.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
searchDGV(TextBox1.Text)
End Sub
Sub searchDGV(ByVal selSearch As String)
With DataGridView1
Dim iTemp As Integer = 1
If .AllowUserToAddRows Then iTemp = 2 '// check if extra row or not, at bottom of dgv.
For i As Integer = 0 To .Rows.Count - iTemp '// loop thru all rows.
For x As Integer = 0 To .Columns.Count - 1 '// loop thru all columns in a row.
If .Item(x, i).Value = selSearch Then '// locate your search.
.Rows(i).DefaultCellStyle.BackColor = Color.Lime
End If
Next
Next
End With
End Sub