Nevermind, after hours of frustration I figured it out. The sendkeys needed to be sent before the openreport method occurs. I was able to get the following example to work with three picklists.
Sub Main()
Dim objImpApp as Object
Dim objImpRep as Object
Set objImpApp = CreateObject("CognosImpromptu.Application"

objImpApp.OpenCatalog "C:\catalog.cat", "Userid","Password"_, , ,TRUE
objImpApp.Visible True
SendKeys "+{End}"
sendkeys "{tab}"
SendKeys "+{End}"
sendkeys "{tab}"
sendkeys "+{end}"
sendkeys "{enter}"
Set objImpRep = objImpApp.OpenReportNoExecute_("C:\report1.imr"

objimprep.retrieveall
objImpRep.Exportdbase("C:\data.dbf"

objImpRep.CloseReport
objImpApp.Quit
set objImpRep = Nothing
Set objImpApp = Nothing
End Sub