You could convert it as text file and using a 1D-lookup-table block. Read further info here CombiTable1Ds

hi Arinomo23

Hello, thank you for your answer
can you explain to me how to write a txt file that Openmodelica accepts.
The excel file contains three columns, the first column corresponds to the time, the second column to the indoor temperature and the last column contains the external temperature

thank you

Basically if you read the link i attached on my prev comment you should write a matrix in text file with a certain format (see the link).

for your case maybe somthing like this:

#1

double TempMatrix (#ofRow, 3)

#time indoorTemp OutdoorTemp

value value value

value value value

value value value

You could just copy paste the values from excel.

Try to play around with 1D-Lookup table on OpenModelica.