You don't need to select the destination file at all. Instead:
/MyFolder\Merge\ecmerge.exe {filepath$} {destpath$}{file$}
You might find using the External Compare and Merge Tools Script even better.
You don't need to select the destination file at all. Instead:
/MyFolder\Merge\ecmerge.exe {filepath$} {destpath$}{file$}
You might find using the External Compare and Merge Tools Script even better.