Hi,
Could someone explain to me how to create, store and manipulate variables please?

At the moment i have this but I get errors:

BUTTONPRESSED DEFINE 0x000000

LDR r4, =BUTTONPRESSED ;Seems to be ok
ADD r4, r4, #1 ;Seems to be ok
MOV BUTTONPRESSED, r4 ;'Operand Syntax Error'

All I want to do is add 1 to the variable 'BUTTONPRESSED' and store it for later use, Thanks