Interpolation function with empty data

Hello everyone, I just got interested in VBA and I seek help from veterans :)
In fact I have a set of data collected for some weeks. Except that there's weeks where there is no data.
I used a VBA function that interpolates the data. Except that the Xarray and Yarray used in this function must not contain null values​​.
function is defined as follows: PINTERP (Xrange, yrange, celulle)
An illustrative Excel file is attached with the VBA code ...

Can you help me on this?

Thank you in advance

This uses a UDF (user defined function). "-" values cannot be used as a data value, Blank or zero is OK, or you can custom format 0 to show "-",

It's working perfectly, just what I need!!!
Thanks a lot for your help mdmackillop...