VS 2010 Need a script which makes combination of some buttons impossible

Hello,

first of all I am new to this forum, so do not blame me for questioning stupid questions :thumb:
I am making a program for chemistry at school.
I have 15 buttons of 'positive' elements and 13 buttons with 'negative' elements,
now the point is that I do not know how I can make script which says I can not combine the 'positive' element buttons with the 'negative' element buttons. Due to this problem, my question will be; How can I do this? :D

something I tried:
Dim PositiveElements as Object

PositiveElements = btnElement1.Text or btnElement2.Text or btnElement3.Text

^this did not do anything, except giving me an error.

Greetings,
KrisO