How to "Grey Out" a customized macro button

Hi,

I have created a macro that I use to save a drawing file in a pdfformat and I assigned it to a custom button on my toolbar.

I am interested in "Greying Out" the button so it only works when adrawing file is open and not a part or an assembly. Is there anyway to do this? That is, I don't want to be able to accdently clickon the button when I am working on a part.SolidworksEdrawings