Two ways of doing this:

1) add an array property during design by simply naming the array aMyArray[1,2] - during run time just treat like a regulary array by dimensioning it to whatever size you need to. The only difference is that you would reference it as so; ThisForm.aMyArray[1,1]

2) add the array during runtime with ThisForm.AddProperty("aMyArray[1,2]", .F.)

Good luck!