The Excel VBA model is different from the Excel reference you need to add to your Acad VBA project...
trying throwing ObjApp infront of your calls..
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ObjApp.Windows("OldFile.xls").Activate
ObjApp.Cutcopypaste = False'<--note this won't work, there is no cutcopypaste, there is CutCopyMode? though.
ObjApp.Range("MetalWork").Copy
ObjApp.Windows("NewTemplate.xls").Activate
ObjApp.Range("MetalWork").Paste
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I haven't run through it, but I'd guess that's your problem