excel - access sub runs once then Error '91': object variable not set -

thank in advance,

i have access database contains following code. setup open defined excel file, locate last row , add 1 value of row in next row below, save etc... first time, if run again "error '91': object variable or block variable not set". however, if hit stop button (reset) in vba window or end button on error message, run again works. i've tried many things , i'm @ loss.

any suggestions?

private sub quotenew1_click()      dim app new excel.application     app.visible = true      dim book excel.workbook     set book = app.workbooks.add("c:\desktop\test_quotes.xlsx")       nextemptyrow  'find last row , add new value next row colum      book.close savechanges:=true      app.quit     set app = nothing  end sub   sub nextemptyrow()     dim emptyrow long      emptyrow = activesheet.usedrange.rows.count      msgbox emptyrow      cells(emptyrow + 1, 1).value = cells(emptyrow, 1).value + 1  end sub 

kind regards,

workbooks.add wants template argument. want use format below adding new workbook first time. after that, want open existing workbook. following code works me , appears meet requirement of adding new row each time incremented value.

private sub quotenew1_click()  dim app new excel.application app.visible = true  dim book excel.workbook  'if workbook exists open it, otherwise create if len(dir("c:\temparea\test_quotes.xlsx")) = 0     'file doesn't exist, create     set book = workbooks.add     app.displayalerts = false     book.saveas filename:="c:\temparea\test_quotes.xlsx"     app.displayalerts = false else     'open existing file     set book = workbooks.open("c:\temparea\test_quotes.xlsx") end if  nextemptyrow  'find last row , add new value next row colum  book.close savechanges:=true  app.quit set app = nothing end sub  sub nextemptyrow() dim emptyrow long  emptyrow = activesheet.usedrange.rows.count  if cells(emptyrow, 1).value = 0     activesheet.usedrange.value = activesheet.usedrange.value + 1 else     cells(emptyrow + 1, 1).value = cells(emptyrow, 1).value + 1 end if  end sub