For hex values which don't actually require a bignum class to work with, you can use the normal conversion function but prefix the number with "&H". VB interprets "&H" in the text as meaning "this is a hex number", just like it does in code.
dim n = Cint("&H" & text)
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…