Try to set up your table like this:
[TABLE="class: grid, width: 500"]
<tbody>[TR]
[TD][/TD]
[TD="align: center"]B
[/TD]
[TD="align: center"]C
[/TD]
[TD="align: center"]D
[/TD]
[/TR]
[TR]
[TD]40[/TD]
[TD]Client Expense
[/TD]
[TD]Client #
[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]41[/TD]
[TD]US $ 500
[/TD]
[TD]Client A[/TD]
[TD]=IF(B41="","",C41&" Expenses: "&B41)
[/TD]
[/TR]
[TR]
[TD]42[/TD]
[TD]US $ 1000[/TD]
[TD]Client B[/TD]
[TD]=IF(B42="","",C42&" Expenses: "&B42)
[/TD]
[/TR]
</tbody>[/TABLE]
Just Drag the formula down to your range.
In case you wish to combine both the expenses in one cell, try this one: =IF(B41="","",C41&" Expenses: "&B41)&". "&IF(B42="","",C42&" Expenses: "&B42)