First, go to Plant, Setup, Layers and add a new layer called Frozen Steel. Make is a color that is truely obnoxious so that it stands out.Next, rather than doing the standard "subtract" command in AutoCAD to make your holes, draw a profile of the hole you want to make, and make it a solid using CADWorx Steel, Plate. Do a COPE to get the hole in the steel. If you have multiple holes, array the solid, then cope. Now, turn the cutting profiles(this is your plate solid) to the "Frozen Steel" layer and turn that layer off. Having the layer turned off means that the objects are still "active" even though they are off. This means that when you stretch, the objects still react to the steel member and retain the hole.
CADWorx has a setting called Auto Cope in Steel, here’s the definition from the help file:
"This command allows the user to set automatic coping on or off. When the system is on and two members are coped, they will remain coped even if one of the member is changed. They will automatically re-cope to the shape of the new member."
By using steel to "cope" the holes into the member rather than a subtract, you can make use of this to keep the holes when you have to stretch a member.
Let me know if it works for you
Theres a short video I made of this on my SkyDrive. Feel free to download and if you have any questions just let me know!