How to use Arrays Using Pic Basic Pro(need help)

[MrSafe]

The code below will compile all I did different from the code on the bottom is change the htxt[x] to x

alpha1:
gosub getkey
LOOKUP key,[" ABCDEFGHIJ"],x
htxt[x] = htxt[x] + 1
RETURN

alpha2:
gosub getkey
LOOKUP key,[" KLMNOPQRST"],htxt[X]
htxt[x] = htxt[x] + 1
RETURN

The code above will not compile the compiler gives me the fallowing error

"output parameter must be a variable"