trigger on opportunity to delete product record of opportunity in salesforce

Please tell me how to do this

I've to write a trigger on "Line_Item__c" object and

field are: Name(Text), Unit Price(Currency), Unit Sold(number), Total Price(Formula:unit_price_c*Unit_sold__c),

 Invoice Statement(Master-Detail:Invoice_Statement__c)

Second Object is "Invoice_Statement__c"

and fields are: Name(AutoNumber), Invoice Value(Roll-up summary:Sum of Total_Price__c field of Line_Item__c),

Account__c(Look-up field: Account) 

Third Object is "Account"

and fields are: Name(Text), Account_Balance__c(Currency)

Now i have to write trigger on "Line_item__c" object to insert total price into Account_Balance__c field of Account.

Please help me if anyone know how to do this.

I've to write a trigger on "Line_Item__c" object and

field are: Name(Text), Unit Price(Currency), Unit Sold(number), Total Price(Formula:unit_price_c*Unit_sold__c),

 Invoice Statement(Master-Detail:Invoice_Statement__c)

Second Object is "Invoice_Statement__c"

and fields are: Name(AutoNumber), Invoice Value(Roll-up summary:Sum of Total_Price__c field of Line_Item__c),

Account__c(Look-up field: Account) 

Third Object is "Account"

and fields are: Name(Text), Account_Balance__c(Currency)

Now i have to write trigger on "Line_item__c" object to insert total price into Account_Balance__c field of Account.

Please help me if anyone know how to do this.