Hello, do you want to solve dimension created at the drawing (associative)?
If you have dim item, you can use ProDrawingDimAttachpointsGet(), which return array of Selections (named ProDimAttachment) – connections at drawing (e.g. to exis, point, …).
So, when you have this Selections you can ‘parse’ them, e.g. get mdlItem by ProSelectionModelitemGet() and analyze this mdlItems as you need.
Or if you somehow have just ProDtlattach attachment point, you can get that Selection with ProDtlattachGet().
On the other hand, if the dim item is not associative Dimension (check by ProDrawingDimIsAssociative()), I am not sure what you need in that case. (The owner of model dim is just by ProDimensionOwnerfeatureGet()).