WOW! I've found a solution!
Dim LD As femap.LoadDefinition
Set LD = App.feLoadDefinition
LD.PutAll(3,FT_SURF_LOAD,FT_NODE,"")
and
LM.LoadDefinitionID = 3
So, LD.loadType needs to be FT_NODE and LD.dataType = FT_SURF_LOAD. This constants will create load definition with type Force on...