VS 2010 Counting number of used textboxes

Hi there,

I have 20 textboxes in a form. I also have a label. All the textboxes are empty, the label text is '0'.
I need the label to count if a textbox is being used, and subtracted if the text in a used textbox is being deleted.

For example, if somebody type in random numbers in five different textboxes, the label must say 5. If the numbers in one of the used textboxes is being deleted, the label must now say 4.

I have been working on the issue for hours now, but I simply can't make it work.
Any help would be deeply appreciated :)

Thanks