Here is the formula I've tried that isn't working:

Â*=concatenate(text(=$c$17-time(1,45,0),"hh:mm"),"Â*",text(=$c$17-time(1,15,0),"hh:mm"))

Is it possible to put these two formulas together? Basically, I need the
time to look like 07:15-07:45. These times pull off of cell C17. If C17 is
changed this range of time needs to change. How do I program excel to do
this?