Send Ctrl-Alt-Del to nested RDP session

eg.
PC - A  = Its your Own Computer
PC - B  = RDP  PC - 1
PC - C =  RDP PC - 2 (Inside RDP PC1)

Here's the scenario: I Remote Desktop from Computer A to Computer B and from Computer B to Computer C.

(1) I want to send Ctrl+Alt+Del to Computer A, I type Ctrl+Alt+Del from Computer A

(2)  want to send Ctrl+Alt+Del to Computer B, I type Ctrl+Alt+End  inside Computer B

(3) If I want to send Ctrl+Alt+Del to Computer C, I open the On-Screen Keyboard on Computer C and use it to type Ctrl+Alt+End, which sends Ctrl+Alt+Del to Computer C

OR  

If I want to send Ctrl+Alt+Del to Computer C, I type Shift+Ctrl+Alt+End  inside Computer C.