Alright, let's cut to the chase. In Windows Applications, there is a Formatting Enabled field for the combobox. This would make this line of code work:

Code:
double calculation = Math.Round((Convert.ToSingle(cmbOutsideDiameter.Text) - (.01299 * Convert.ToSingle(txtPercentOfThread.Text) / Convert.ToSingle(txtThreadsPerInch.Text))), 3);
HOWEVER, I am now duplicating this program in a hand-held device and the compact framework doesn't have the Formatting Enabled field. The error I am getting because I cannot turn the Formatting Enabled thing on is, Format Exception is unhandled.