Nested INDIRECT Command Not Populating Correctly

Please refer to my screenshot.

The formula in question is:
=N$4*VLOOKUP($B5,'BOM MATRIX'!$A$2:$AJ$500,INDIRECT("N3"),FALSE)
which is currently keyed into cell N5

what I'm trying to do is to populate rows sideways so for example the formula in cell O5 should be:
=O$4*VLOOKUP($B5,'BOM MATRIX'!$A$2:$AJ$500,INDIRECT("O3"),FALSE)

problem is whenever I copypaste. The first part (N$4-> O$4) populates correctly while INDIRECT("N3") remains the same even though it should be INDIRECT("O3") instead

Is there anything I can do to fix this?