Returns the number of dimensions in a safearray object
(vlax-safearray-get-dim var)
An integer identifying the number of dimensions in var. An error occurs if var is not a safearray.
Set sa-int to a single-dimension safearray with one dimension:
(setq sa-int (vlax-make-safearray vlax-vbinteger '(1 . 4))) #<safearray...>
Use vlax-safearray-get-dim to return the number of dimensions in sa-int:
(vlax-safearray-get-dim sa-int) 1