Group Wise Incremental Calculation

[srvu]

Source

No Al_No Amt
X1 1 20
X1 2 30
X1 3 40
X1 4 50
X2 1 60
X2 2 20

I have a source as above

Data that shud be populated in Target

No Al_No Amt Prev_buffer_Amt
X1 1 20 0 (shud be)
X1 2 30 20
X1 3 40 50 (sum of prev amts (20+ 30))
X1 4 50 90 (group wise calculations (20+30+40))
X2 1 60 0
X2 2 20 60

Data in Column Prev_buffer_amt shud be the Prev records sum amt (group by NO). For 1st records Prev_amt will be Zero.For 2nd record Prev_amt shud be the 1st record amt,
For 3rd record, sum of (1st and 2nd records amts)......

Can it be calculated in Expression Transformation?

kindly help....

 

[srvu]

I got answer from the post given by MacLeod72 on running totals..
Port 1: KEY Input
Port 2: VAL Input
Port 3: V_TOTAL Variable Exp: IIF(KEY != V_KEY, VAL, V_TOTAL + VAL)
Port 4: V_KEY Variable Exp: KEY
Port 5: RUNNING_TOTAL Output Exp: V_TOTAL

Thanks to MacLeod72