Windows 7 Remapping Numpad Keys to Function as Application-Specific Shortcuts with AutoHotkey

How can I remap the Numpad numbers to mirror function key settings defined by the application program I am running. For example, the program defines F2 as CTRL+A, which it then uses to toggle a program setting.

Using AutoHotkey I can put
Numpad1::send ^a
and Word/Notepad do react properly to a Numpad1 keypress - for their definition of ^a = select all.

However the application program does not recognise the key remapping. It won't even recognise the simpler:
Numpad1::send 9
Nor a hopefull attempt of
Numpad1::send F2

Can anyone help?