C# information in datagirdview column is flickering

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C#

DataGridView

I am a beginner programmer developing a C# WinForms solution in VS 2015 Professional for my school.

After I implemented the code below, the information on column 9 of the DataGridView is flickering and causes the fields on my form to gray out. It displays correctly only after I drag and move the form around the screen.

Can you please take a look at my code and see what the problem is? The code does what I want, but I am sure it can be perfected. Thank you. I really appreciate your time and help.

What I have tried:

private void alunos_detDataGridView_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
     try
     {
        decimal midtermGrade = Convert.ToInt32(this.alunos_detDataGridView.Rows[e.RowIndex].Cells[3].Value);
        decimal finalGrade = Convert.ToInt32(this.alunos_detDataGridView.Rows[e.RowIndex].Cells[4].Value);
        decimal oralGrade = Convert.ToInt32(this.alunos_detDataGridView.Rows[e.RowIndex].Cells[5].Value);

        this.alunos_detDataGridView.Rows[e.RowIndex].Cells[9].Value = ((midtermGrade + finalGrade + oralGrade) / 3);

         if (alunos_detDataGridView.CurrentRow.Cells[0].Value.ToString() != null)
         {

             if ((midtermGrade + finalGrade + oralGrade / 3) >= 60)
             {
                 this.alunos_detDataGridView.Rows[e.RowIndex].Cells[10].Value = "Aprovado";
             }
             else
             {
                this.alunos_detDataGridView.Rows[e.RowIndex].Cells[10].Value = "Reprovado";
             }
         }
     }
     catch
     {
     }