The situation here, is that you use bars of material, for example, and you want to use them in units of length (metres, say). But, your supplier wants you to buy in terms of weight (kilos, say).

You can arrange things so all the necessary conversion are done for you automatically.

To do this you just define the usual length of the material in its material record and specify the weight of a unit length of that material. For example, if you buy stainless steel bars in 3 metre lengths, specify the usual length as 3 Metres and specify the weight of 1 Metres. The system then has enough information to convert between length and weight whenever needed.