Hi I am writing a large program where I am using three text boxes. I am
performing validation controls on these text boxes however there are
some conditions

Names of textboxes
1.    x
2.    y
3.    z

The conditions are

1.    x , y , z should be numeric.
2.    x and y can be blank ( x = "" , y = "") at a time
3.    z can never be blank, it should always have a numeric value.
4.    if x has a value y cannot be blank and x should be non negative
5.    if y has a value x cannot be blank and y should not be non negative.
6.    if x and y have values y > x
7.             z should be non negative

A message box should pop up each time the user clicks a button with the
appropriate error ( eg : x cannot be negative , or y cannot be greater
than x , etc... )

Since I am actually dealing with cells in a data grid I cannot use any
sort of validation controls. I need to perform the validation using
code. I am using visual studio 2005 , Visual Basic
Any sort of help will be gratefully appreciated.