I hope I understand Your question correctly.

PT100 is a platinum RTD which has a temperature versus resistance property which is stable , repeatable and well defined.

So in order to utilise PT100 sensor You will need an external interface circuit to generate say a voltage proportional to resistance.

You can then use analogue input to read in this voltage. You can then use the Look up table capability of LDmicro to translate resistance to temperature.

The other option is to use mathematical capabilities of LDMicro and solve the equation which defines RTD resistance and its temperature.

The supplier of Your RTD element should be able to give You an idea what the formula looks like.