C# and touchscreen

Question

Hello, I am working on an application that uses touch screens. I am going to have to provide an on screen number pad to allow user input. The problem is that I have multiple data input fields that the user will have to select. So the number pad will be used for multiple input controls. How do I create the number pad so that the selected control does not lose focus and the user can enter a multi-character string into the control? Hope I'm being clear - thanks for any help.