Thanks, Luciano
My macro now looks like thus:
Code:
TXArray	var Sample_Array
TXIndex	var word SYSTEM
TXData	var word SYSTEM
@TX_Sample macro index
	@ MOVE?WW index, TXIndex
	TXData = TXArray[TXIndex]
	Hserout [TXData / 100, TXData // 100]
	@ endm
(Sample_Array is a word array that I'm using to store my data in).

This works great, and I can call it like this:
Code:
	@ TX_Sample _Sample
Thanks for the pointers, fellow PBPers. The only thing I couldn't do was get it to take both the array and the index as arguments.... I have to nut out the whole memory addressing thing in my head before I can get it to work.