I have something similar where the information from the first Listbox determines the contents of the subsequent Listbox(s)
We use the InteractiveChange method of the first Listbox to build/select the relevant data:

create cursor curProcess2 (type c(1),freq c(1),desc c(35),last d(8),payroll c(15))

do case
case condition1....
      insert into curProcess2 values (.....)
case condition2....


etc


with thisform.cbo2
	if !empty(.displayvalue)
		.displayvalue =""
	endif
	.rowsourcetype=6
	.rowsource    ="curProcess2.desc,last"
	.columncount  =2
	.columnwidths ="200,60"
endwith