MDG UIBB - Can´t change Dimensions

[Cnv88]

Hi Community!!

I´ve created extensions to incorporate custom fields at screen, MATERIAL entity, to restrict extension to specific CR type and material type. Now I wanted to change dimensions assigned and option is not available (at MARCBASIC I have other extension and in same part is allowed to change but is same fot both).

Option to change dimentsions is always greyed out. 

Any idea? 

Thanks!