怎样获取表？

' get the first table in the table on contents dim ptabcollection as istandalonetablecollection dim psttable as istandalonetable dim pdisptable2 as idisplaytable dim pttable as itable set ptabcollection = pmap if ptabcollection.standalonetablecount = 0 then msgbox "must have atleast one table" exit sub end if

pmap并没有赋给ptabcollection 什么，于是出现"must have atleast one table"的错误，应怎样修改？？？ 请帮帮忙！！！