Subtraction in PowerBi matrix Aggregation

Hello,

I have a table with the following contents:

Header Subheader Subheader2 Amount
     A            B                C               10
     A            B                D               20

This is then represented as a power bi matrix:

Header   Amount
     A          30
       B        30
         C      10
         D      20

I have a situation which requires the aggregation to roll up to a subtraction rather than an addition. So the value of B should be C - D (10 - 20) instead of (C + D) without reversing the sign of D. So the matrix should look like:

Header   Amount
    A           -10
      B         -10
        C        10
        D        20

Any DAX measure I can create to achieve this?