[Fizzlemizz]

It's certainly possible but a bit more context about what you want to achieve might help you get some more specific information.

Edit: The most basic (rough as guts) is you have a frame with 3 buttons. In the OnClick event for button A and B.

For A:

  self:GetParent().A_Clicked = true
  if self:GetParent().A_Clicked and self:GetParent().B_Clicked then
     --show button C
     self:GetParent().A_Clicked = nil
     self:GetParent().B_Clicked = nil
  end

For B:

  self:GetParent().B_Clicked = true
  if self:GetParent().A_Clicked and self:GetParent().B_Clicked then
     --show button C
     self:GetParent().A_Clicked = nil
     self:GetParent().B_Clicked = nil
  end

Very rudimentry and open to refinement depending on requirement.