If you pass an argument by reference when calling a procedure, the procedure access to the actual variable in memory. As a result, the variable's value can be changed by the procedure.

If you pass an argument by value when calling a procedure, the variable's value can be changed with in the procedure only outside the actual value of the variable is retained.

Passing by reference is the default in VBA. If you do not explicitly specify to pass an argurment by value, VBA will pass it by reference.

Argument Passing ByVal

Describes passing arguments by value, which means the procedure cannot modify the variable itself.

Argument Passing ByRef

Describes passing arguments by reference, which means the procedure can modify the variable itself.