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Is there a way to specify a pin to read through a constant or variable?

I'd like to write a program where I setup the pin assignments through constants or variables.
For example, you can write something like:

sda con p18
scl con p19

and then latter reference:

"high sda" instead of typing "high p18"

What I can't figure out is how to read a pin setup as an input in a similar way.
From what I can tell the pin variables "inxx" where xx is the pin number have to explicitly reference the pin number. I'd like to use something like "in(sda)" which would be equivalent to "in18" in this example.

Is there a way to do this that I'm missing? My goal is to declare the pin assignments at the beginning of a program and then have the rest of the program reference these assignments.

After playing around a little bit, I found the following method...

Lets say you want to read SDA on pin 16. You can read INL0 (contains input values for pins 0 to 31) into a variable and shift right 16 digits and always read bit 0 of the result.

SDA_Read = INL0 >> SDA
SDA_Value = SDA_Read.Bit0

It works, but the overhead makes my overall bit banged I2C function* take about 2.5 times longer than an otherwise slow I2C read. Any ideas on how to lessen the overhead or another approach?

* This is being done to support a non-standard slow sensor which doesn't work with the built-in SW I2C functions and probably wouldn't even work with HW I2C because of the speed. The sensor also has a complete inability to change its address, and there is a desire to support 2 of these sensors which requires they be placed on different input pins.

You can also use individual IN# variables which access the individual pins(eg IN16)

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