two ways
1.
A B C
1 Type Amount balance
2 credit 100.00 100.00
3 Debit 50.00 =If(a3="Debit",b2-b3,b2+b3)
4 debit 10.00 =If(a4="Debit",b3-b4,b3+b4)
2.
A B C
1 Debit Credit balance
2 100.00 100.00
3 50 =if(b3="",a3-b2,b3+b2)
4 10 =if(b4="",a4-b3,b4+b3)