Remember, the original question was How to return to calling code, not return from calling code, for example, you set a breakpoint on an api and you want to see who or where the api was called from. That is where you would use F11.
On a side note: (so there is no confusion)
Taken straight from Softice's help file.
Default Function Key Assignments
F1 = H;
F2 = ^WR;
F3 = ^SRC;
F4 = ^RS;
F5 = ^X;
F6 = ^EC;
F7 = ^HERE;
F8 = ^T;
F9 = ^BPX;
F10 = ^P;
F11 = ^G @SS:ESP;
F12 = ^P RET;
SF3 = ^FORMAT;
AF1 = ^WR;
AF2 = ^WD;
AF3 = ^WC;
AF4 = ^WW;
AF5 = CLS;
AF11=dd dataaddr->0;
AF12=dd dataaddr->4;