Conditional Formating Based On Other Cells Being Blank

Hello All - I've had trouble finding a solution for my specific issue and have attempted a variety of conditional formatting methods with little to no success.

In the attachment I am trying to force the user to fill in all the necessary fields before an end result registers. Those fields highlighted in yellow are "required" (Note: Aside from B15:16, it is really the calculation in B18 that is needed, anything input before it just calculates into a sum there).

Based upon the fields input, preliminary results will be yielded in B18 and B30 (green highlight next to these cells), these values then translate to B34:B35 and final result of the larger of the two generates in B37. I do not want a value to register in B37 in red until both B34/35 have a value registered. Text should remain white until both fields have an entry.

Help please!