Run Macro When Cell Condition/Criteria Met

Two ranges A1:A20 (input values) and B1:B20 (results).

Input values are always the digit 1 which starts the calculation and the result comes up in the cell to the right.

Example:
Input (1) in cell A1 gives a result value in cell B1.
Input (1) in cell A12 gives a result value in cell B12.
I need a macro �StartCalc� to do the following thing:
Go to cell A1.
Put in the value �1�
Check the result cell B1.
If �result value� > 20, then run macro �Test� (this macro is working)
Go to cell A2.
Put in the value �1�
Check the result cell B2.
If �result value� > 20, then run macro �Test� (this macro is working)
��.
Go to cell A20.
Put in the value �1�
Check the result cell B20.
If �result value� > 20, then run macro �Test� (this macro is working)
End of macro.