Thanks JPN. So, I added "void calculate();" under the public slots inside window.h.

I then added the two connections (with the correction of "lcd2" to "this", I assumed), under my "Window::Window()" inside the window.cpp and added at the end the "void Window::calculate() {.....}"

First time run, it crashed - something not working with QLCDNumber.h it said. I changed that and instead of sending the value to an LCD, I used
Qt Code: 
  1. qDebug("Val12 = %.4f", valJ1+valJ2)
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to check what's going on...

In the debug window, I do get "Val12 = 0". The good part is that "Val12 = 0" reappears everytime I change something in the two spinboxes. The sad part is that it just doesn't have the correct value - stays zero. I suppose that "calculate" is done every time I change something in one of the two spinboxes, the valueChanged connection works OK, but valJ1 and valJ2 don't get the value of their spinbox from the valueSpinBoxJ1/2->value thing... which is not good at all... how can that be?

WHAT'S WRONG!?!?!?!

X-man