First of all, I use a custom function written by Mikhail Edoshin, BitIsSet( Number, Bit ).

// Returns whether or not the binary bit in the given number is turned on. i.e., ~BitIsSet( 16; 5 ) would return True as 16 is 10000 in
// binary. Similarly, ~BitIsSet( 18; 2 ) would also return True as 18 is 10010 in binary. This calculation is thanks to Mikhail Edoshin
// and is found at http://edoshin.skeletonkey.com/2005/11/custom_function.html.
//
// Written by Mikhail Edoshin

Mod( Div( Number; 2 ^ ( Bit – 1 ) ); 2 )

Next I have a set of custom functions that are simply constants, such as kModifierShift:

// Used as a named constant. Should have a value such that ModifierKeyIsActive( kModifierShift ) = True when the shift key is held down.

1

kModifierCapsLock is 2, kModifierControl is 3, etc, each value corresponding to the bit tha

t’s true from GetActiveModifierKeys.

Finally, I have ModifierKeyIsActive( ModifierKey ), which accepts one of those constant custom functions:

// The ModifierKey parameter should be an integer between 1 and 5. These can be accessed via the kModifier* custom function
// constants. Returns whether or not the given modifier key, as specified by it’s power of two equivalent, is held down at the time
// the function is evaluated.
//
// EXTERNAL REQUIREMENTS: The BitIsSet custom function. Easiest to use with the presence of the kModifier* custom function
// constants.
//
// Written by Charles Ross

BitIsSet( Get( ActiveModifierKeys ); ModifierKey )

With the above, I get code that looks quite nice: If[ ModifierKeyIsActive( kModifierShift )]