If you have four columns, you can have
A1= Bought B1=Cost C1=Paid In D1= Running Total.
In D2, enter the current figure owed.
In D3, enter the following,
=IF(AND(B3="",C3=""),"",(D2+(B3*1.0295)-(C3*0.97)))
If you know what auto fill is, do that for the rest of column D. If you don’t know what that is, highlight D2, move the cursor until you see a wee ”+” in the bottom right corner and drag it down as far as you want. That will paste the formula in the rest of the column.
The “IF” and “AND” bit of the formula is so that it shows blank when there are no figures in both columns.