Modifying column references

[rsbyers01]

How can I copy a formula in Sheet 1 A1 that reads =Sheet 3!C$3-Sheet3!D$3 from cell A1 to cell A2 and automatically change the column reference 2 columns to the right so it looks like like =Sheet3!E$3-Sheet3!F$3 after it is copied to
A2?

thanks for your help!