Error in Straight table by using variable

[#1]

Hi

I created a variable like this

vDiff=sum(Premium1)-sum([Premium2])

I created a striaght table with dimentions includeing Premium1 and Premium2.

For difference I gave as =VDiff. It is showing error as shown in attachment.

Please help

[tresesco]

For long term solution and learning read this blog: the-magic-of-variables

If you want adhoc help, try to share your sample app.