holding items

You could use FindChild(parent_mesh, child_name$) to get a handle to the bone:
mesh = LoadAnimMesh("something.b3d")
bone = FindChild(mesh, "handbone")
There is also GetChild, which requires an index.

Then, assign this bone as a parent to the object:
EntityParent pickobject, bone

Finally, probably you should move it a bit using MoveEntity.

If you don't know the name of the hand's bone, try this program to enlist all children:

Graphics3D 800, 600, 0, 2

mesh=LoadAnimMesh("mak_robotic.x")

printoutchildren(mesh)

Function printoutchildren(mesh)

	Print EntityName$(mesh)

	For i = 1 To CountChildren(mesh)
		g=GetChild(mesh, i)
		printoutchildren g
	Next
	
End Function