Filtering Gallery by LookUp Column with calculated field through search textbox

[PowerNinja]

Hi Power People,

Is there a way to filter my gallery by searchTextbox that has a lookup Table with Calculated Column? In my MainGallery I have inside another gallery to show this lookup Table column with the list of names and want to filter by these names.

Filter(FOAS, StartsWith(CellSiteList.SearchSiteName, txtSiteSearchFOA.Text)

If I search It's returning blank gallery?

The second gallery property items = Filter(FOA_CELLS, FOA.Id = ThisItem.Id).SearchSiteName

and is showing all the related list of sites but now I want to specifically filter my Main gallery with this data.