Item Cross Ref and the UITM Field

We have a large customer for which we have populated their Items in the F4104 Item Cross Ref.

When we enter orders for them, we can use the #xxxxxx format in the SO Detail UITM field to use their item numbers and when the line is processed, it converts it to standard LITM.

We see the UITM field in many other applications (P41202, P3002, P4021) and wondered if there was any way for those apps to use an Item Cross Ref value versus just the Short, Second and Third items using the \ and * prefix.