C#, If Statement, Min and Max

A = .8-(Y/3)/10.0;

int Holder = Y, A=.8;
while (Holder > 0)
{
    A-= .1;
    Holder-= 3;
}

If Y<3
    A=.8
 Else if Y < 6
    A=.7
 Else if Y < 9
    A=.6

if(Y <= 3.0)      A = ...;
else if(Y <= 6.0) A = 0.7;
else if(Y <= 9.0) A = 0.6;
...

int temp = Y / 3;
float A = 0.8f - (temp / 10f);

if ((cb5_1.Checked)&&(cb5_2.Checked)&&(cb5_3.Checked))
		{//if the first three text boxes are checked calculate based on the following.
			decimal a, b, c, z;
			decimal aa, bb, cc, zz;
			a = decimal.Parse(cbx5_1a.Text);
			b = decimal.Parse(cbx5_2a.Text);
			c = decimal.Parse(cbx5_3a.Text);
			aa = decimal.Parse(cbx5_1q.Text);
			bb = decimal.Parse(cbx5_2q.Text);
			cc = decimal.Parse(cbx5_3q.Text);
			z = (aa+bb+cc);

			if (z = > 3)
			{
				zz = ((a*aa)+(b*bb)+(c*cc))*.7m;
			}
			else if (z = > 6)
			{
				zz = ((a*aa)+(b*bb)+(c*cc))*.6m;
			}
			else if(z = > 9)
			{
				zz = ((a*aa)+(b*bb)+(c*cc))*.5m;
			}
			tb5_atotal.Text = Math.Round(z,2).ToString();

if ((cb5_1.Checked)&&(cb5_2.Checked)&&(cb5_3.Checked))
{
    //if the first three text boxes are checked calculate based on the following.
    decimal a, b, c, d, z;
    decimal aa, bb, cc, zz;
    a = decimal.Parse(cbx5_1a.Text);
    b = decimal.Parse(cbx5_2a.Text);
    c = decimal.Parse(cbx5_3a.Text);
    aa = decimal.Parse(cbx5_1q.Text);
    bb = decimal.Parse(cbx5_2q.Text);
    cc = decimal.Parse(cbx5_3q.Text);
    z = (aa+bb+cc);

    d = 0.8m - ((z / 3) / 10m);

    zz = ((a*aa)+(b*bb)+(c*cc))*d;

    tb5_atotal.Text = Math.Round(z,2).ToString();

if Y <= maxValue then
    if Y >= minValue then
        return value
    else
        follow minLink
else
    follow maxLink