[Joe Ross]

Here is how I would implement the code (from which you should be able to figure out how to implement your code with pointers)

void toggle_single_solenoid(unsigned char button, unsigned char *prev_button, unsigned char *relay_fwd)
{
   if (button && !prev_button)     //don't keep toggling if they hold the button
      *relay_fwd = !(*relay_fwd);

   *prev_button = button;
}

call it like this:

 toggle_single_solenoid(p1_sw_trig, &prev_p1_sw_trig, &relay1_fwd);

Remember to declare prev_p1_sw_trig and change the variables to whichever switches and relays you want.