dim db as new adob.connection
dim rs as new adob.recordset
dim subTotalValue as long
db.connection="your conection string"
db.open
set rs=db.execute("Select sum(subtotal) from <your table>")
subTotalValue=rs.fields(0).value
rs.close
db.close
Hope this solves your problem
If it didnt hit
http://www.nairaland.com/nigeria/topic-60292.0.html and explain your questions there, if need be I will write a sample and sent it to you.
Take care and bye for now.