SSRS 2008 Work order report , in sub total donot want to add the 0 level in ( how to add the expression )

working in Work order report, this report has different level , for example

0 level transaction

1 level transaction

in subtotal don't want to add 0 level transaction,

when I did the sub total it added all the level , so in sub total amount double up because of that

how to add the expression so I can the level 0 take out from sub total , so it does not include in sub total

can some one please help me with this

thanks in advance