Hi,
Nah, I don't think that's it...
CIVA must be a variable and they are not case sensitive. Had it been a string it should have been "CIVA" vs "civa"

As a test, ditch the calculations and try:
Code:
f3 = $01
f4 = $28
SEROUT2 CIVP,CIVS,[$FE,$FE,civa,$E0,$14,$01,f3,f4,$FD]      ' Send this to the radio for NEW VOLUME setting (no $)
In this particular case you do not want the $-sign because then it'll send the hexadecimal numbers F3 and F4 and not the content of the variables f3 and f4. Having the $-sign in there would have made the above statement send 243 ($f3), 244 ($f4) instead of 1 ($01), 40 ($28).

/Henrik.