You don't need macro substitution.

pdmVar.temppath = GetEnv("TEMP")+"\PDM Docs\"
If !DIRECTORY(pdmVar.temppath) Then
	MD (pdmVar.temppath)
EndIf

>This code works fine:
>
>

>temppath = "'" + GetEnv("TEMP")+"\PDM Docs\" + "'"
>If !DIRECTORY(&temppath) Then
>	MD &temppath
>EndIf
>

>
>But when I try to get away from using the Public var temppath with following code I get an error that second line of code is missing a ')'.
>
>

>pdmVar.temppath = "'" + GetEnv("TEMP")+"\PDM Docs\" + "'"
>If !DIRECTORY(&pdmVar.temppath) Then
>	MD &pdmVar.temppath
>EndIf
>