Web Forms :: Calculate Value When Dropdown Changed?

I have 2 dropdown list.On selectedindex changed I am assigning the selected value in to a label

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
string sltvalitem1 = DropDownList1.SelectedValue.ToString();
lblitem1price.Text = sltvalitem1.ToString(); // item 1 price
int itm1 = Convert.ToInt32(lblitem1price.Text); // item 1 price in to interger
int itmtotal = itm1 ; // total value in to the integer
lblitem1price.Text = itmtotal.ToString();
}
protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
{
string sltvalitem2 = DropDownList2.SelectedValue.ToString();
lblitem2price.Text = sltvalitem2.ToString();// item 2 price
int itm2 = Convert.ToInt32(lblitem2price.Text);
int itmtotal2 = itm2; // total value in to the integer
lblitem2price.Text = itmtotal2.ToString();
}

So now in lblitem1price I have one value and lblitem2price I have dropdownlist2 value.

so I want to calculate these 2 values in to a Label called lbltotal.

So then according to the selected value of 1st or 2nd drop down total should be changed.