Issue with formula on conditional formatting

hello there!

I have an issue when using conditional formatting to highlight cells with certain conditions.

Here's my situation:

I have a workbook where Sheet1 has cells with values only. There are no formulas.
On Sheet2, I have the following formula on some cells:

=IF(Sheet1!A1<>"",Sheet1!A1,"")

Obvioulsy, the cell name varies as I copy and paste the formula on the lower cells.

I tried to use conditional formatting on Sheet2 so as to highlight cells using 2 conditions:

1- create borders around cells with a formula
2- create a yellow pattern on those cells whose formula DID NOT result in an empty cell.

If you see the image attached to this post, you'll see the 2 conditions I have set up on Excel 2003 conditional formatting feature.

The first condition is based on the following code I embedded on my workbook:

Function IsFormula(cell_ref As Range)
IsFormula = cell_ref.HasFormula
End Function

The second one is also based on that code/formula, and shows what I thought to be the condition I was looking for (to highlight in yellow all cells whose formula DID NOT result in an empty cell. However, only the first seems to be working. Can someone help me? Maybe I've made a mistake on condition 2.