Find nearest value in column greater than X (variable)

jeyare  You should be able to do this with the MINX function, however the part where you want to use a slicer won't work with a calculated column: https://excelwithallison.blogspot.com/2020/09/reporting-order-of-operations.html

In order for it to update with slicers, you'd need to create them as a MEASUREs

Evaluation =

VAR _CurrentAgeIndex = SELECTEDVALUE(DataTable[Age Index])

VAR _AgeIndexDiff = SELECTEDVALUE(SlicerTable[Diff])

RETURN

MINX(FILTER(DataTable, DataTable[Age Index] >= _CurrentAgeIndex + _AgeIndexDiff ),  DataTable[Age Index] )

Evaluated Weight =

VAR _CurrentAgeIndex = SELECTEDVALUE(DataTable[Age Index])

VAR _AgeIndexDiff = SELECTEDVALUE(SlicerTable[Diff])

VAR _Evaluation = 

MINX(FILTER(DataTable, DataTable[Age Index] >= _CurrentAgeIndex + _AgeIndexDiff ),  DataTable[Age Index] )

RETURN

MINX(FILTER(DataTable, DataTable[Age Index] = _Evaluation), DataTable[Weight] )

Thx Allison,

works great with some tunes, when I calculate MIN and MAX values to find the nearest possible difference in ABS value (+ or -)