Oscar,

I am afraid you will have to produce more coding, e.g. what are the other conditions.
otherwise check in the debugger for the defined variables when you reach #7

Your coding syntax as such works, however I had to change as follows:
and please note I dont like the use of your abbrevation m as variable definition at all

with thisform
	for lnI = 1 to 7
		lnCnr = "(" + allt(str(i)) + ")"
		.addobject("Cal" + lnCnr, "DiaCalendario2", i, "thisform.lblDesc", m.luM, pkNov)
		.addobject("Enc" + lnCnr, "EncabDia")             && ERROR HERE WHEN i=7 ONLY
		.Cal(lnI).move((lnI-1) * 50 + px, py + 22)
		.Cal(lnI).visible = .t.
		.Enc(lnI).move((lnI-1) * 50 + px, py)
		.Enc(lnI).visible = .t.
	endfor
endwith

Regards,

Koen