Selectively Copying Cells Based On Column Header?

I'm trying to copy cells from a column in one workbook to cells in a column in another workbook based on what's in a header column.

Such as

Original workbook
Mat Qty
A 1
C 3
D 2
E 4
G 5
Total 15

Target workbook becomes

Mat Qty -> Mat Qty
A -> A 1
B -> B
C -> C 3
D -> D 2
E -> E 4
F -> F
G -> G 5

My code so far (which might not be worth reading) is:

Code:
Sub CopyColumnToWorkbook()
Dim sourceColumn As Range, targetColumn As Range, sourceColumnValue As Range, targetColumnValue As Range
Dim mySourceCell As Range, myTargetCell As Range

[code].....

I'm getting a runtime error ('1004'. Application-defined or object-defined error) on the Copy statement within the If sttement.